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  Subjects -> PHYSICS (Total: 754 journals)
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PHYSICS (546 journals)            First | 1 2 3 4 5 6 | Last

Doklady Physics     Hybrid Journal   (Followers: 1)
Dynamical Properties of Solids     Full-text available via subscription  
ECS Journal of Solid State Science and Technology     Full-text available via subscription   (Followers: 1)
Egyptian Journal of Remote Sensing and Space Science     Open Access   (Followers: 5)
EJNMMI Physics     Open Access  
Embedded Systems Letters, IEEE     Hybrid Journal   (Followers: 18)
Energy Procedia     Open Access   (Followers: 3)
Engineering Failure Analysis     Hybrid Journal   (Followers: 27)
Engineering Fracture Mechanics     Hybrid Journal   (Followers: 18)
Environmental Fluid Mechanics     Hybrid Journal   (Followers: 2)
EPJ Nonlinear Biomedical Physics     Open Access  
EPJ Quantum Technology     Open Access  
EPJ Techniques and Instrumentation     Full-text available via subscription  
EPJ Web of Conferences     Open Access  
European Journal of Physics     Full-text available via subscription   (Followers: 4)
European Journal of Physics Education     Open Access   (Followers: 5)
European Physical Journal - Applied Physics     Full-text available via subscription   (Followers: 4)
European Physical Journal C     Hybrid Journal  
Europhysics News     Open Access   (Followers: 1)
Experimental Mechanics     Hybrid Journal   (Followers: 16)
Experimental Methods in the Physical Sciences     Full-text available via subscription  
Experimental Techniques     Hybrid Journal   (Followers: 30)
Exploration Geophysics     Hybrid Journal   (Followers: 3)
Few-Body Systems     Hybrid Journal  
Fire and Materials     Hybrid Journal   (Followers: 5)
Flexible Services and Manufacturing Journal     Hybrid Journal   (Followers: 1)
Fluctuation and Noise Letters     Hybrid Journal   (Followers: 1)
Fluid Dynamics     Hybrid Journal   (Followers: 5)
Fortschritte der Physik/Progress of Physics     Hybrid Journal  
Frontiers in Physics     Open Access   (Followers: 2)
Frontiers of Materials Science     Hybrid Journal   (Followers: 4)
Frontiers of Physics     Hybrid Journal   (Followers: 1)
Fusion Engineering and Design     Hybrid Journal   (Followers: 2)
Geochemistry, Geophysics, Geosystems     Full-text available via subscription   (Followers: 21)
Geografiska Annaler, Series A: Physical Geography     Hybrid Journal   (Followers: 3)
Geophysical Research Letters     Full-text available via subscription   (Followers: 46)
Geoscience and Remote Sensing, IEEE Transactions on     Hybrid Journal   (Followers: 20)
Glass Physics and Chemistry     Hybrid Journal   (Followers: 2)
Granular Matter     Hybrid Journal   (Followers: 2)
Graphs and Combinatorics     Hybrid Journal   (Followers: 6)
Handbook of Geophysical Exploration: Seismic Exploration     Full-text available via subscription  
Handbook of Metal Physics     Full-text available via subscription  
Handbook of Surface Science     Full-text available via subscription   (Followers: 3)
Handbook of Thermal Analysis and Calorimetry     Full-text available via subscription  
Haptics, IEEE Transactions on     Hybrid Journal   (Followers: 4)
Heat Transfer - Asian Research     Hybrid Journal   (Followers: 6)
High Energy Density Physics     Hybrid Journal   (Followers: 1)
High Pressure Research: An International Journal     Hybrid Journal   (Followers: 1)
IEEE Journal of Quantum Electronics     Hybrid Journal   (Followers: 15)
IEEE Signal Processing Magazine     Full-text available via subscription   (Followers: 27)
IET Optoelectronics     Hybrid Journal   (Followers: 2)
Il Colle di Galileo     Open Access  
Indian Journal of Biochemistry and Biophysics (IJBB)     Open Access   (Followers: 4)
Indian Journal of Physics     Hybrid Journal   (Followers: 4)
Indian Journal of Pure & Applied Physics (IJPAP)     Open Access   (Followers: 8)
Indian Journal of Radio & Space Physics (IJRSP)     Open Access   (Followers: 5)
Industrial Electronics, IEEE Transactions on     Hybrid Journal   (Followers: 11)
Industry Applications, IEEE Transactions on     Hybrid Journal   (Followers: 5)
Infinite Dimensional Analysis, Quantum Probability and Related Topics     Hybrid Journal  
InfraMatics     Open Access  
Infrared Physics & Technology     Hybrid Journal  
Intelligent Transportation Systems Magazine, IEEE     Full-text available via subscription   (Followers: 1)
Intermetallics     Hybrid Journal   (Followers: 4)
International Applied Mechanics     Hybrid Journal   (Followers: 2)
International Geophysics     Full-text available via subscription   (Followers: 3)
International Journal for Computational Methods in Engineering Science and Mechanics     Hybrid Journal   (Followers: 8)
International Journal for Ion Mobility Spectrometry     Hybrid Journal   (Followers: 1)
International Journal for Simulation and Multidisciplinary Design Optimization     Full-text available via subscription   (Followers: 1)
International Journal of Abrasive Technology     Hybrid Journal   (Followers: 2)
International Journal of Aeroacoustics     Full-text available via subscription   (Followers: 6)
International Journal of Applied Electronics in Physics & Robotics     Open Access   (Followers: 1)
International Journal of Astronomy and Astrophysics     Open Access   (Followers: 3)
International Journal of Computational Materials Science and Surface Engineering     Hybrid Journal   (Followers: 7)
International Journal of Damage Mechanics     Hybrid Journal   (Followers: 5)
International Journal of Fatigue     Hybrid Journal   (Followers: 7)
International Journal of Fracture     Hybrid Journal   (Followers: 8)
International Journal of Geometric Methods in Modern Physics     Hybrid Journal   (Followers: 1)
International Journal of Geophysics     Open Access   (Followers: 3)
International Journal of Heat and Fluid Flow     Hybrid Journal   (Followers: 9)
International Journal of Low Radiation     Hybrid Journal  
International Journal of Low-Carbon Technologies     Open Access   (Followers: 1)
International Journal of Mass Spectrometry     Hybrid Journal   (Followers: 12)
International Journal of Material Forming     Hybrid Journal   (Followers: 2)
International Journal of Materials and Product Technology     Hybrid Journal   (Followers: 4)
International Journal of Mechanical Sciences     Hybrid Journal   (Followers: 5)
International Journal of Mechanics and Materials in Design     Hybrid Journal   (Followers: 5)
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology     Open Access   (Followers: 4)
International Journal of Micro-Nano Scale Transport     Full-text available via subscription   (Followers: 2)
International Journal of Microstructure and Materials Properties     Hybrid Journal   (Followers: 7)
International Journal of Microwave Science and Technology     Open Access   (Followers: 2)
International Journal of Modeling, Simulation, and Scientific Computing     Hybrid Journal   (Followers: 1)
International Journal of Modern Physics A     Hybrid Journal   (Followers: 1)
International Journal of Modern Physics B     Hybrid Journal  
International Journal of Modern Physics C     Hybrid Journal  
International Journal of Modern Physics D     Hybrid Journal  
International Journal of Modern Physics E     Hybrid Journal   (Followers: 1)
International Journal of Nanomanufacturing     Hybrid Journal   (Followers: 1)
International Journal of Nanoscience     Hybrid Journal   (Followers: 1)
International Journal of Nanotechnology     Hybrid Journal   (Followers: 5)
International Journal of Non-Linear Mechanics     Hybrid Journal   (Followers: 4)

  First | 1 2 3 4 5 6 | Last

Journal Cover Handbook of Geophysical Exploration: Seismic Exploration
   Follow    
   Full-text available via subscription Subscription journal
     ISSN (Print) 0950-1401
     Published by Elsevier Homepage  [2572 journals]   [SJR: 0.103]   [H-I: 2]
  • Chapter 5 Detection of Transient Phenomena Due to Active Scatterers
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Recent discoveries of slow slip events and intermittent occurrence of deep non-volcanic tremors in the subduction zones are believed to be caused by the movement of deep crustal fluids that are mainly composed of supercritical water and supplied by the dehydration of the subducted slab, although the physical mechanisms of their occurrence await further investigations. Intermittent occurrence of these events suggests that the stress conditions in the crust and upper mantle could be a critical state for generation of these events triggered by the movements of deep crustal fluids. The heterogeneity in the lithosphere originated from both the stress state and heterogeneous distribution of fluid bearing rocks can be candidates of “scattering sources” of seismic and electromagnetic waves traveling through earth’s interior. Temporal variations of the scattering sources are the essential characteristics of seismogenic regions as well as the active volcanic regions, so that they can be called the “active scatterers”. The active geophysical monitoring with a method precise and stable enough must be an essential tool to detect and clarify such an evolving process related to the temporal changes that are governed by the structure sensitivity, and may presumably be associated with the movement of the fluid mainly composed of supercritical water in the crust and upper mantle conditions. Among many structure sensitive phenomena, probable changes in the transmitted seismic or electromagnetic signals could be detected by means of the temporal variations of impedance and anisotropic dispersion of the media or by correctly imaging the characteristics of the “active scatterers” with structure sensitive properties in the subduction zones.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 23 Detection and Continuous Monitoring of Strong Seismic
           Reflectors at the Subducting Philippine Sea Plate Using ACROSS Methodology
           
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      In order to examine the validity of the Accurately-Controlled Routinely-Operated Signal System (ACROSS) to detect temporal changes of reflective signatures, we conducted a nine-month experiment using a seismic ACROSS in Toki city and a temporal linear seismic array extending toward the south from Toki city. The seismic experiment was carried out from December 2005 to September 2006. The observations show that 8-days stacking at ∼60 km offset distances showed similar prominent arrivals as 30-days stacking. This suggests that ∼ one-week stacking can be used to detect some prominent arrivals up to ∼60 km offset distances. The waveform characteristics of the ACROSS records are equivalent to the downhole seismometer records used in the High-net seismological network. By calculation of theoretical travel times and synthetic seismograms using the re-analyzed crustal structural model, we compared the observed seismograms together with theoretical travel times and synthetic seismograms. Synthetics and observed records fit nicely, but unfortunately the reflected arrivals from the subducting plate boundary are absent in the used receiver range. However, 8-days stacking of received data at a station “OSD” located in 61.2 km provides a high enough signal-to-noise ratio (S/N) to identify Pg, which is the crustal refracted wave, and shallow reflected arrivals.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 24 Active Seismic Monitoring of the San Andreas Fault at Parkfield
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      A unique data set of seismograms for 720 source-receiver paths has been collected as part of a controlled source Vibroseis experiment at the San Andreas Fault (SAF) in Parkfield, California. In the experiment, seismic waves repeatedly illuminated the epicentral region of the expected M6 event at Parkfield, from June 1987 until November 1996. For this effort, a large shear-wave vibrator was interfaced with a three-component (3-C) borehole High-Resolution Seismic Network (HRSN), providing precisely timed collection of data for detailed studies of changes in wave propagation associated with stress and strain accumulation in the fault zone (FZ). Data collected by the borehole network were examined for evidence of changes associated with the nucleation process of the anticipated M6 earthquake at Parkfield. These investigations reported significant travel-time changes in the S coda for paths crossing the fault zone southeast of the epicenter and above the rupture zone of the 1966 M6 earthquake. Analysis and modeling of these data—and comparison with observed changes in creep, water level, microseismicity, slip-at-depth and propagation from characteristic repeating microearthquakes—showed temporal variations in a variety of wave propagation attributes, variations that were synchronous with changes in deformation and local seismicity patterns. The main lesson learned from the Vibroseis experiment is that changes were clearly observable in the locked part of the SAF, which has relatively little natural seismicity and could hardly be used for monitoring of travel-time and attenuation changes. The heavily instrumented, creeping part of the SAF northwest of Parkfield is not expected to accumulate stress. Monitoring of this region revealed no significant changes in seismic signatures. Remarkably, in 2004, the expected M6 earthquake at Parkfield occurred and nucleated well into the locked SAF section, well to the southeast of the Vibroseis/HRSN monitoring experiment primarily centered on Middle Mountain. This result suggests that active seismic monitoring can be a useful tool for detecting stress changes associated with the nucleation of larger earthquakes, even when event observations are made over nucleation zones with low natural seismicity. Numerical modeling studies and a growing number of observations have argued for the propagation of fault-zone guided waves (FZGW) within the SAF zone that is 100 to 200 m wide at seismogenic depths and with 20% to 40% lower shear-wave velocity than the adjacent unfaulted rock. FZGW are also capable of assessing the degree of fault continuity and other complex FZ geometries, such as fault jogs. The SAF in the Cholame Valley, where a 2004 M6 earthquake nucleated, is characterized by such complexity. Because FZGW also primarily propagate within the core of fault zones, active continuous seismic monitoring, using guided waves, is our proposed solution for earthquake studies in the Parkfield area.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 22 Singular Value Decomposition in Active Monitoring Data Analysis
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      An algorithm based on SVD is presented in this paper to retrieve travel times and attenuation factors from observed data of the Accurately Controlled Routinely Operated Signal System (ACROSS) which is modeled as superimposed exponentially damped sinusoids in a limit band of frequency. The algorithm is validated using numerical and field test data. In a numerical simulation, the algorithm is successfully applied to analyze the structural dispersion of a Rayleigh wave. In the field test, the algorithm is used to process ACROSS data and get almost the same result as those from hammer hit data by a traditional multi-filter method.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 10 EM-ACROSS System and Corresponding Tensor Transfer Functions in
           Diffusion Field Region
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      We have developed a new electromagnetic controlled-source method for the monitoring of electrical states in the ground. It is called EM-ACROSS (electromagnetic - accurately controlled routinely operated signal system). The basic idea of EM-ACROSS can be used in any frequency range. We have developed one application of the system using two pairs of current dipoles at the Tono area for a survey below 500 Hz, where the electromagnetic field behaves as a diffusion field. We have carried out a field test using this application, and acquired an extremely accurate tensor transfer function from the source to the receiver, where the distance from the source is about 950 m. For a few months from the phase of the transfer function, we could see a correlation with rainfall.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 11 Design and Workout of ACROSS Transmitters Using Air Bearings
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      The generation and extraction of heat due to inherent friction at the ball bearings to support the large force is an important technical problem in current seismic ACROSS transmitters of the rotary type for stable maintenance and routine operation for continuous active monitoring over years. This paper proposes the use of gas bearings to improve the relevant situation, since they are expected to be useful in reduction of heat generation and energy loss to eliminate the peripheries for heat extraction. Since no experience has been reported so far to sustain the eccentric rotor by gas bearings, we made some test experiments of eccentric rotors supported by air bearings, and we confirmed that they are ideal for supporting the centrifugal force generated by rotation of an eccentric rotor for the ACROSS transmitters of the next generation, if it is designed appropriately to meet our utility purposes.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 21 Effect of Spatial Sampling on Time-lapse Seismic Monitoring in
           Random Heterogeneous Media
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      From the viewpoint of spatial sampling in time-lapse seismic surveys, we reveal the effects of scattered waves on subsurface monitoring by using a numerical simulation of the seismic wave field and comparing the different responses of the final section by applying two different types of data processing: conventional CMP stacking and poststack migration. We consider a seismic waveform consisting of incoherent scattered waves generated by random isotropic heterogeneity, which is a noise-like wave field caused by multiple scattering of seismic waves. We employed the finite difference method for modeling a 2-D acoustic wave field in random heterogeneous media. Our numerical experiments indicate that the highly dense spatial sampling does not improve the resolution of the difference section between base and monitor surveys when the subsurface structure contains random heterogeneity. We demonstrate the existence of a small but significant difference by differentiating two sections with different spatial sampling. This small difference is attributed to the truncation artifact which is due to geometrical limitation and that cannot be practically prevented during data acquisition. This difference causes numerous complicated events over the whole section in heterogeneous media, even when the interval of spatial sampling becomes shorter than the Nyquist sampling interval,and degrades seismic difference sections if the spatial sampling interval of base survey is not identical to that of monitor survey.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 19 Foundations of the Method of EM Field Separation into Upgoing
           and Downgoing Parts and its Application to MCSEM Data
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      The renewed interest in the methods of electromagnetic field decomposition into upgoing and downgoing parts is generated by the practical problem of removing the effect of EM airwaves on marine controlled source electromagnetic data collected in shallow water. In this paper we consider the principles of solving this problem using the classical methods of EM field separation into external and internal parts. We demonstrate that the most general approach to upgoing/downgoing field decomposition is based on the theory of Stratton-Chu type integrals. This approach allows us to separate the field observed on an arbitrary surface. In the case of a flat observational surface, the Stratton-Chu method is equivalent to the decomposition technique based on the Fourier transform in the spatial frequency domain. We present also a novel method of EM field separation using the method of horizontal gradients of the EM field. The new technique is tested on synthetic MCSEM data. The numerical results show that stable and reliable separating results can be obtained using this new approach. We demonstrate also that the method represents a useful tool for a rapid qualitative interpretation of MCSEM data.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 20 Automatic Travel Time Determination from a Frequency-domain
           Transfer Function: The Sompi Event Analysis
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      We have developed a method to extract “events” localized in a time domain from a transfer function in the frequency domain, which is a part of the basic analysis in ACROSS (Accurately-Controlled Routinely-Operated Signal System). In response to the limitations with respect to the practical application shown in the previous procedure, we designed a revised version of this method, based on maximum likelihood estimation. The basic theory, including the revision, is presented here, along with a practical procedure for automatic travel time determination. We then submitted this revised version to a numerical test, the results of which supported the validity of this method for analysis of transfer functions involving plural “events” in the time domain.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 17 Maxwell’s Equations and Numerical Electromagnetic
           Modeling in the Context of the Theory of Differential Forms
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      In the framework of classical theory, the electromagnetic field is described by the electric and magnetic vector fields, and Maxwell’s equations represent a system of differential equations with respect to these vector fields. An alternative approach to the formulation of Maxwell’s equations is based on the algebraic theory of differential forms, and it results in a very compact and symmetric system of differential form equations. I demonstrate in this paper that Maxwell’s equations appear naturally from the basic equations for the differential forms. The basic laws of electromagnetism are actually imprinted in the fundamental differential relationships between the vector fields and differential forms. The new equations contain the differentials of the flux and work of the electric and magnetic fields. This fact indicates that the electric and/or magnetic flux and work should be treated as the major characteristics of the EM field, instead of using the conventional vectorial representations. The differential form approach corresponds well to geophysical experiments, which involve, as a rule, the measurement of the flux and the work (or voltage) of electric and magnetic fields. It is shown that a similar approach can be used for effective numerical modeling of EM fields as well.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 18 3D Electromagnetic Holographic Imaging in Active Monitoring of
           Sea-Bottom Geoelectrical Structures
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      We consider an application of the ideas of electromagnetic (EM) holography/migration to the interpretation of a typical marine controlled-source (MCSEM) survey, which consists of a set of sea-bottom receivers and a moving electrical bipole transmitter. The 3D interpretation of MCSEM data is a very challenging problem because of the enormous amount of computations required in the case of the multitransmitter and multireceiver data acquisition systems used in these surveys. At the same time, we show that MCSEM surveys with their dense system of transmitters and receivers are extremely well suited for application of the holography/migration method. The combined EM signal in the receivers forms a broadband EM “hologram” of a sea-bottom geological target. As in optical and radiowave holography, we can reconstruct the volume image of the geological target by “illuminating” this EM hologram with a reference signal. The principles of holography/migration imaging formulated in this paper are tested on typical models of a sea-bottom petroleum reservoir. We also apply this new technique to the interpretation of an MCSEM survey conducted in the Troll West Gas Province (TWGP), offshore Norway.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 4 Seismic Active Monitoring System Concept
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      We present the concept and design lay-out of a 4-D long-term coherent, precisely controlled, seismic signal transmission system continuously monitoring the Lithosphere in space and elapsed time for Earth parameter changes. New-technology seismic vibrator sources coherently and continuously emit mutually uncorrelated, maximum-energy point-force signal codes simultaneously from different permanent locations. The signal codes covering the 0-5 Hz or broader or higher frequency bands are continuously repeated for indefinite time. At existing permanent and portable seismic stations, the corresponding particle displacement signals are retrieved by long-term time- and phase-coherent stacking and quadrature matched filtering with the emitted force pilot signal. The resulting complex-envelope seismograms consisting of the dual time series of instantaneous amplitude and instantaneous phase reflect the Earth’s impulse response or Green’s function. The signal code lengths can be selected to accommodate the arrivals of primary and later seismic phases. Signal synchronization and coherence are sustained by tying all sources and receivers to an accurate Universal Time standard. Precise signal arrival detection and timing are achieved by a novel algorithm operating on coherent ensembles of the instantaneous phase seismogram. The algorithm relates the timing error standard deviation (TESD) to signal-to-noise ratio (SNR). The TESD ranges from less than 0.5 ms at 36 dB or higher seismogram SNR to less than 0.5 s at −6 dB SNR. The ray paths of primary and later seismic phase arrivals from three or more uncorrelated sources yield a grid for ray-tracing/travel-time tomography and contrast-source imaging. Extrapolation of existing hydraulic seismic vibrator data suggests that two weeks of continuous, coherent signal transmission, stacking, and processing of 50 kN peak force vibrator signals provide sufficient signal-to-noise ratio to cover ray path ranges of 200-500 km.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 3 Elements of Active Geophysical Monitoring Theory
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      The surface dilatancy zone is a phenomenon found in computational experiments, namely the loosening process of extensive zones within the upper Earth’s crust under the action of tangential and tensile tectonic stresses near the surface. This purely mechanical phenomenon is of special interest to earthquake prediction: specifically, it enables a quantitative approach to calculating fracturing characteristics (an “integral precursor” of seismic activity) using data from a variety of geophysical fields. Physical models of integral precursors are being developed. These models are the space-time functions of the crack density within developing earthquake sources and anomalous geophysical fields on the Earth’s surface. Such models are obtained by solving the multidisciplinary (combined) inverse problems for corresponding geophysical fields (e.g., the field of displacements and deformations on the Earth’s surface, the field of electric conductivity, anomalies in the gravitational field and the groundwater level). To precisely locate the zones of likely seismic activity in the Earth’s crust, we propose a dynamic tomography method, developed within the framework of the scalar wave equation, and a numerical approach for optimizing the evaluation of dilatancy zones. A vibroseismic monitoring scheme for the “source” and dilatancy zones is discussed in detail. In this scheme, we use powerful vibrators, having the force of 50, 100, and 250 tons, and recording systems that can accumulate signals over long periods, to obtain seismograms at distances of up to 400 km and records of monofrequency signals at distances of up to 1000 km. Using mathematical modeling, we estimate the sensitivity of the active monitoring method for detecting small changes in seismic wave density and velocity in some of the geologic media. We show that it is possible to detect relative changes in seismic wave velocity of about 10- 5-10- 6 in the internal zone with a radius of 10 km, using a vibromonitoring system made up of a 100-ton vibrator and a recording system with 50-100 km offset.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 16 Nonlinear Processes in Seismic Active Monitoring
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      One of the methods used to monitor the development of geodynamic processes in seismically active zones is based on regular sounding of the geological medium by powerful seismic vibrators, with subsequent analysis of the time dynamics of the seismic field parameters. Such monitoring is accompanied by some nonlinear processes taking place during the radiation and propagation of seismic waves. One of these processes results from peculiarities in the design of different vibrators and their interaction with the ground. Other processes develop in the medium during seismic wave propagation. Such processes enrich the seismic wave field with additional lower and higher frequency components. In this paper, we show that accounting for these processes increases the noise immunity of vibrational correlograms (analogues of explosive seismograms), as well as their time resolution, contributing to more accurate arrival-time measurements of the main wave. Broadening the spectra of the initial seismic signal can result from the seismic nonlinearity of fractured dilatancy regions, which are typical of potential earthquake zones. Here, we show the applicability of seismic nonlinearity as a possible predictive characteristic of the earthquake source development process. Results, analysis, and conclusions presented in this paper are based on numerical calculations and field experiments. The experiments were conducted in parallel with the monitoring of a 355 km long seismic profile during periods of lunar-solar tides. We show that taking into account the amplitude ratios between the multiple and fundamental harmonics of seismic wave fields enables the independence of monitoring results from seasonal and instrumental variations. At the same time, the high sensitivity of these ratios to small stress variations in the Earth’s crust is retained.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 14 Signal Discrimination of External Geomagnetic Effects Using the
           Transfer Function Approach with Continuous Wavelet Transform
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      External-source geomagnetic variations in the ULF band ( f
      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 15 Development of Simulation Algorithm for Analyzing Temporal
           Stability of ACROSS Seismic Source
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Temporal stability of the ACROSS seismic source is a very important feature for active geophysical monitoring to detect small changes related to the target region. The stability of the source depends on the shallow ground properties. Therefore, it is necessary to estimate the effects of the temporal changes of the shallow ground properties on the source’s motion and the excited waves. Then we try to estimate its effects by numerical simulation. In this paper, first, we review two examples of the temporal changes observed in the experiments and discuss the required properties of the simulation algorithm. According to the discussion, we develop a simulation algorithm for calculating the source’s rigid motion and its generated waves. In this algorithm, the ACROSS seismic source and the ground are modeled as a horizontally forced rigid circular disk and a multilayered media, respectively. The solution of displacement excited by a horizontally forced rigid circular disk in a multilayered media is derived by applying the explicit Green’s function approach to the solution of a horizontal point force. We also carry out simple numerical simulation to investigate the effects of the shallow ground properties on the excited waves and the source’s rigid motion in a simple case, using the program developed in this research.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 13 Secondary Calibration Method of Seismometers by Utilizing
           ACROSS Signal
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      We have developed a technology for active monitoring of seismogenic zones and/or volcanic areas. The technology utilizes Accurately-Controlled Routinely-Operated Signal System (ACROSS) and is capable to detect subtle changes in physical properties. It also requires optimal placement of source and receiver arrays containing many easy-to-use seismometers. However, any current calibration method determining a frequency response of the ground motions for such seismometers is not accurate enough. We developed a secondary calibration method for easy-to-use seismometers by utilizing seismic ACROSS signals, a vibration table and reference accelerometers. We present the basic concept together with technical steps, and demonstrate the experimental results for 52 target uni-axial sensors by using the more reliable accelerometers as reference. Despite the average accuracy of the frequency responses for the reference sensors, we could easily obtain a precise enough frequency response for each tested sensor using the Maximum Likelihood method. In experimental results, the accuracies of frequency response for sensors were approximately 102-103. Although these values are not accurate enough for active monitoring of the Earth’s interior, we can conclude that this method is useful enough to provide a simultaneous and precisely-determined frequency response for a large array of easy-to-use seismometers.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 2 Large-scale Geophysical Surveys of the Earth’s Crust Using
           High-power Electromagnetic Pulses
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Deep electromagnetic (EM) study of the earth’s crust requires the use of a powerful controlled source of the EM field. In this paper, we present a concept of the application of multimegawatt EM pulses generated, for example, by self-contained MHD facilities of short-term operation (3-12 s), for geophysical and geological surveys. We describe the physical and engineering background of pulsed MHD facilities fueled by a solid propellant of 10-100 MW of electric power, developed in Russia. The paper also summarizes the results of experimental and methodological studies performed during the last 30 years in different regions of Russia, Kirghizia and Tajikistan. The results of this development provided the foundation of a new technology for deep geoelectrical exploration of hydrocarbon reservoirs on land and offshore.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 1 Seismicity Precursors for Active Monitoring of Earthquakes
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      The M6.0 2004 Parkfield and M7.0 1989 Loma Prieta strike-slip earthquakes—on the San Andreas Fault (SAF)—were preceded by seismicity peaks occurring several months prior to the main events. Earthquakes directly within the SAF zone were intentionally excluded from data because they manifest stress-release processes rather than stress accumulation. The observed increase in seismicity is interpreted as a signature of the increasing stress level in the surrounding crust, whereas the peaks and the subsequent decrease in seismicity are attributed to damage-induced softening processes. Furthermore, in both cases there was a distinctive zone of low seismic activity that surrounded the epicentral region in the pre-event period. The increase of seismicity in the crust surrounding a potential future event, and the development of a low-seismicity epicentral zone, can be regarded as promising precursory information that could help signal the arrival of large earthquakes. The Gutenberg-Richter relationship (GRR) should allow extrapolation of seismicity changes down to seismic noise level magnitudes. This hypothesis is verified by comparison of seismic noise at 80 Hz with the Parkfield M4 1993-1994 series, where noise peaks ∼5 months before the series to about twice the background level. The found mid-term precursors can potentially trigger an active monitoring that could enable accurate forecasting of catastrophic earthquakes.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 9 Acquisition of Crosswell Seismic Monitoring Data
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Crosswell seismic acquisition provides an ideal geometry for monitoring travel-time changes in the subsurface. Analysis of delay time in terms of a characteristic frequency allows us to estimate optimal acquisition parameters (frequency and distance). We have deployed standard data acquisition equipment for continuous monitoring of crosswell travel time in two separate field experiments, with well spacings of 3 and 30 m. The acquisition hardware used for the field experiments is described, along with environmental effects (such as temperature) that impact the measurements. Two field experiments are described that correlate changes in travel time (and therefore velocity) with changes in barometric pressure. The results from the two field sites show pressure sensitivity for velocity of 10−6/Pa to 10−8/Pa.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 8 Active Geophysical Monitoring of Hydrocarbon Reservoirs Using EM
           Methods
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Marine controlled-source electromagnetic (MCSEM) technology has been successfully established as an effective tool for offshore hydrocarbon (HC) exploration. In this paper we consider another application of the MCSEM method for HC reservoir monitoring. We demonstrate that EM methods can be successfully used for the monitoring of production wells in connection with the enhanced recovery of hydrocarbons. We have developed a powerful new EM modeling technique based on the integral equation method with an inhomogeneous background conductivity (IE IBC). This new method, and the corresponding computer software, make it possible to model the EM response over a realistic complex model of a sea-bottom HC reservoir. The numerical modeling results demonstrate that the MCSEM method has the ability to map changes in resistivity caused by the production of hydrocarbons over time. In addition, the EM data help to visualize changes in the location of the oil-water contact within a reservoir. This result opens the possibility for practical application of the EM method in HC reservoir monitoring.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 12 Stacking Strategy for Acquisition of an ACROSS Transfer
           Function
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Development of a powerful stacking technique is important in active monitoring in order to effectively enhance the signal-to-noise ratio (SNR) by utilizing not only quiet nighttime data but also noisy daytime data. Here we propose a stacking technique for data obtained by the Accurately Controlled Routinely Operated Signal System (ACROSS) with a reasonable method for noise level evaluation. An essential point is that the SNR would enhance by data stacking in reciprocal proportion to the square root of the observation time period. We show an application of this stacking method to real seismic and electromagnetic data obtained at our observation test site of ACROSS.


      PubDate: 2012-12-15T09:27:58Z
       
  • Volume contents
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40




      PubDate: 2012-12-15T09:27:58Z
       
  • Preface
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40




      PubDate: 2012-12-15T09:27:58Z
       
  • Contents
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40




      PubDate: 2012-12-15T09:27:58Z
       
  • Copyright
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40




      PubDate: 2012-12-15T09:27:58Z
       
  • Index
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41




      PubDate: 2012-12-15T09:27:58Z
       
  • References
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41




      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 6 Fluid Flow and Recovery
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41

      In the previous chapter, we discussed the reservoir properties and numerical reservoir simulation in detail; however, the bases of numerical reservoir simulation are fluid flow and the material balance equations, which determine the flow of fluids in the reservoir and govern the recovery factor. These equations are used by reservoir engineers for interpreting and predicting reservoir performance.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 5 Reservoir Geophysics Some Basic Concepts
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41

      Reservoir geophysics plays an important role to bridge the two important disciplines of science, viz., geophysics and reservoir engineering. In the current scenario, these two fields are so intertwined that anyone involved in exploration and exploitation of natural hydrocarbons needs to understand the basic concepts of geophysics and reservoir engineering. This chapter is aimed at providing a brief overview of hydrocarbon reservoirs and the properties of the rocks and fluids associated with such reservoirs. Also, fractal behavior of some of the physical properties is discussed. The chapter will serve as a basic guide to those who have no background in reservoir geophysics or petroleum engineering.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 4 Seismic Reservoir Monitoring
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41

      Seismic reservoir monitoring is normally done by comparing the results of repeated seismic reflection surveys over the same area. This technique is known as time lapse or four-dimensional (4D) seismic, where the fourth dimension is time. 4D reservoir monitoring involves acquisition, processing, and interpretation of repeated seismic data over a field to monitor the changes occurring in the reservoir either due to production of hydrocarbons or enhanced oil recovery/improved oil recovery (EOR/IOR)-related changes, such as injection of water/gas, steam, polymer, etc., into the reservoir. EOR has been defined in Chapter 6, citing real field examples. The basic principle of time-lapse seismic reservoir monitoring is to subtract out the first-order static geology part to produce clear images of the time-variant fluid flow changes. The reference survey in 4D is termed as baseline and repeated surveys are termed as monitor surveys. This technique helps to identify unswept oil and gas zones in the reservoirs. The idea behind its application is to generate a time-lapse difference dataset, which should be close to zero, except in the reservoir where changes have occurred. The reservoir properties may change due to change in saturation of rock fluids under the effect of production or EOR/IOR. For example, if oil is being produced under water flooding conditions, then saturation of both oil and water changes in the reservoir. This will lead to a change in the seismic response of the reservoir. Apart from saturation, the reservoir may undergo pressure changes either due to production or an EOR/IOR process. Change in pressure will lead to changes in seismic velocities. In general, the expected time-lapse change in the reservoir is small; hence, good quality control is required for 4D monitoring.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 3 Fractal Inversion
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41

      Inversion of seismic data plays a vital role in reservoir characterization. High-resolution inversion methods provide models with higher resolution than those built from the conventional stacked seismic traces (e.g., Rowbotham et al., 2003; Sen, 2006). Such models are good for reservoir characterization and model building. Edited well logs provide the most accurate and the best vertical resolution of geophysical information of a subsurface reservoir. Though vertical resolution of well logs is very good, horizontal resolution is poor because of sparse availability and the small extent of lateral depths of investigation. One approach to obtain a high-resolution 3D description of a reservoir is to use geostatistical interpolation, extrapolation, or simulation (Hass and Dubrule, 1994) using available well-log data at a few sparse locations. Accuracy of such models is dictated by the number and spatial distribution of the wells over a reservoir. Therefore, seismic data being the most continuous information available (although at a lower vertical resolution), a stochastic inversion of seismic data that integrates seismic data and well-log data can add great value in reservoir characterization (Francis, 2006a) as it combines seismic data with well logs and uses vertical resolution from well logs and good horizontal resolution from seismic data into the estimated model. The fusion of seismic and well-log data is possible using seismic inversion, which converts seismic data information into petrophysical properties such as acoustic impedance and shear impedance (e.g., Dimri, 1992; Russell and Hampson, 2006; Srivastava and Sen, 2010; Vedanti and Sen, 2009). Merging seismic data directly with well-log data is difficult because they have a different range of scale/frequency of measurement compared to well logs and also their recording is basically in a different domain, viz., seismic data in the time domain, whereas logs are recorded with depth.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 2 Structural Modeling Using Fractals
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41

      Geologists provide models of the Earth's subsurface based on the exposed outcrops and other geological inputs. Providing a reliable model of the Earth's subsurface in terms of structural setting and property variations is the main objective of the investigations by earth scientists. With the advent of sophisticated geophysical techniques, it is possible to integrate the geophysical observations with the geological models to constrain them better and evolve a more realistic model. Several scattered studies (Yu and Li, 2001) have shown that the rock matrix follows fractal behavior from micro- to mega-scale. Geological models can be made using discrete objects, voxels, or surfaces that honor geological and geophysical observations. We present a geophysical modeling technique based on Voronoi tessellations, which honors available geophysical data, viz. horizons from seismic and physical properties derived from well logs, seismic data, and other kinds of geophysical data.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 1 Introduction of Fractals Application to Gravity and Magnetic
           Data
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41

      The classical geometry deals with objects of integer dimensions. Zero-dimensional points; one-dimensional lines; two-dimensional planes, like squares; and three-dimensional solids, such as cubes, make up the world as we have previously understood it, but many natural phenomena like a length of coast line and the shape of clouds are better described with a dimension partway between two whole numbers. To describe such irregular shapes, fractal geometry was coined, which describes the noninteger or fractal dimensions. So while a straight line has a dimension of one, a fractal curve like a rocky coast line will have a dimension between one and two depending on how much space it takes up as it twists and curves. The more that fractal fills a plane, the closer it approaches to two dimensions. So a fractal landscape made up of a large hill covered with tiny bumps would be close to the two dimensions, while a rough surface composed of many medium-sized hills would be close to the three dimensions (Peterson, 1984). Fractal geometry is a compact way of encoding the enormous complexity of many natural objects. By iterating a relatively simple construction rule, an original simple object can be transformed into an enormously complex one by adding ever increasing detail to it. The essence of fractal theory lies in fractional dimensions.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 7 Reliable Measurement Method to Reveal a Peculiar Dielectric
           Dispersion in Wet Rocks by Means of ACROSS
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      A precise and reliable method for complex dielectric permittivity measurement was developed using the data processing method ACROSS (accurately controlled routinely operated signal system) and aids in electric circuit and electrode installation to reduce bias in measurement. By using the method, we succeeded in clarifying that moist quartz grains and glass beads cause such strong dielectric dispersion that dielectric permittivity increases in reciprocal proportion to frequency and exceeds 105 at 1 mHz. The loss angle was of the order of 10- 2 radians relatively independent of frequency which suggests the possibility that a moist crust has a significant dielectric effect that can be detected by EM prospecting methods in the future.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 6 Active Vibromonitoring: Experimental Systems and Fieldwork
           Results
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Experiments with powerful low-frequency vibrators have been carried out to determine the sensitivity of an active vibroseismic monitoring system to small changes in seismic wave velocities within the Earth’s crust. Three component recording systems were located 356 km from a 100-ton-force seismic vibrator. Radiation sessions involving monofrequency and sweep signals were repeated every 3 h over 8 days, enabling the finding of tide variations in the amplitudes and phases of the recorded signals and wave arrival times. Both 12-hour and 24-hour periodicities were detected in the recorded spectra. The experiment showed that an active monitoring system is capable of detecting relative variations in the seismic wave velocities on the order of 10- 5-106, within a 300-400 km area around the source, and performing direct monitoring of stresses in this area, to determine the regions and phases of critical stress as an earthquake precursor. At present, vibroseismic interferometry is being used for active monitoring of the Lake Baikal region, over an area 550 × 250 km. The method is based on seismic sounding of the region by powerful seismic vibrators with durable (up to 1 h) radiation of narrow-band monofrequency signals. The changes in the stressed-deformed state are determined through variations in the signal’s amplitude-phase characteristics, using data recorded by regional seismic stations and mobile recording complexes.


      PubDate: 2012-12-15T09:27:58Z
       
  • Series Page
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41




      PubDate: 2012-12-15T09:27:58Z
       
  • Acknowledgments
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41




      PubDate: 2012-12-15T09:27:58Z
       
  • Preface
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41




      PubDate: 2012-12-15T09:27:58Z
       
  • Copyright
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41




      PubDate: 2012-12-15T09:27:58Z
       
  • Dedication
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41




      PubDate: 2012-12-15T09:27:58Z
       
  • Foreword
    • Abstract: 2012
      Publication year: 2012
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 41




      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 25 Characteristics of ACROSS Signals Transmitted from the Tono
           Transmitting Station and Observed by Hi-net
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Monitoring the temporal variation of physical properties around the plate boundary region is important for detecting subtle changes before the occurrence of a large earthquake. However, few studies have been done that involve continuously monitoring seismic waves. ACROSS is a newly developed tool for monitoring the temporal variation in seismic waves with high accuracy. In this study, using signals transmitted from the Tono seismic ACROSS station, we evaluate seismograms and check the validity of ACROSS signals observed at Hi-net seismic stations deployed by NIED. Using ACROSS signals, we tested our capability for detecting temporal variations in travel times for P and S waves. A clear onset can be observed in stations up to about 60 km apart. The wave train of P and S waves vary from station to station, suggesting that the effect of local velocity structure under the station is large within the frequency range used (10-20 Hz). The temporal variation in transfer function is also investigated, with transfer functions calculated every 10 days for about one and half years. A clear temporal change above the noise level, apparently an annual variation, is observed at the N.HOUH station. This variation, the cause of which is not clear at this time, indicates the possibility for detecting temporal variations in waveforms using ACROSS signals.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 26 Active Monitoring Using Submarine Cables—Leveraging
           Offshore Cabled Observatory for Passive Monitoring
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Eight seafloor are observatories installed in Japanese water. Passive monitoring by these observatories has revealed a number of qualities that include detailed micro-earthquake activity before and after plate-boundary earthquakes, the existence of micro-tsunamis, the capability of early detection of tsunamis, the importance of seafloor geodetic observations, etc. These new findings were brought about by passive, real-time and continuous time series of earthquake and tsunami records acquired on the seafloor. Recently, our knowledge about earthquake source mechanisms has revealed the possibility of the detection of spatiotemporal changes in physical properties that may occur at inter-plate boundaries, and active seismic surveys have found reflection amplitude differences at seismically inactive plate boundaries or possible seismic asperities. We propose that the detection of such physical property changes becomes possible when we combine seafloor observations and active seismic sources dedicated to the precise monitoring of reflection amplitudes at plate boundary interfaces.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 27 Seasonal Changes in Vibroseismic Monitoring Experiments in
           Siberia
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      We present the results of a long-term experiment involving vibroseismic monitoring of the Earth’s crust, which began in 1997 in the Thom’-Kolyvan’ fold zone. Two vibrators of 100- and 40-ton force were used as excitation sources. One three-component (3C) sensor was placed 3 m under the source platform, while another 3C sensor was located at the Novosibirsk Seismological Station, 49 km from the vibrators. Data were collected periodically during several years. The seasonal variations in the frequency characteristic of the vibrator radiation have been investigated. Freezing and thawing of the ground was found to have an effect on vibrator radiation, such that there are distinct winter and summer radiation patterns generated by the vibrator (as well as transition periods in between). The seismograms from the remote zone also reveal cyclical changes in winter and summer. Travel-time wave attributes do not vary with freezing or thawing of the ground, while the dynamic behavior of recorded traces has a pronounced correspondence with freezing or thawing for different years. More detailed research has found that the freezing and thawing of the ground affect not only the radiation spectrum, but also the directional diagram of the source.


      PubDate: 2012-12-15T09:27:58Z
       
  • Chapter 28 Estimates of Crustal Stress Sensitivity in the Lake Baikal
           Region, from Active Vibroseismic Monitoring and Solid Earth Tide Data
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40

      Short-term active vibroseismic monitoring was conducted to evaluate the crustal stress sensitivity of seismic velocity in the Baikal rift zone. Knowledge of stress sensitivity is required for interpreting long-term active vibroseismic monitoring results and predicting the stress state of the crust in potential earthquake zones. The elastic Earth tide is a natural calibrator of variations in internal stresses in the Earth’s crust. Our ultimate goal is to find a relationship between variations in seismic velocity and wave amplitudes and the inner-crust stress changes. Seismically active zones under Lake Baikal that extend over 125.5 km have been illuminated by low-frequency vibrations repeated every 2 h over a period of 2 weeks. The source was a stationary powerful vibrator that generated a force amplitude of about 100 tons within a 5-10 Hz frequency range. The received signals were transformed to cross-correlation functions in an online mode. Our analysis showed variations in the travel times and wave amplitudes of seven different waves, which were compared to the elastic Earth tide. Our main focus was on the inner-crust waves, including the reflection from the Moho boundary and from the top of the upper mantle. Despite the unique high precision of the variation measurements (about 10−5 for travel times), any statistically significant correlations with Earth tides were not found. However, arrival data enabled us to calculate an upper limit for possible velocity stress sensitivity, which falls far short of that predicted by previous researchers. Principal sources of error included not only external noise, but also small, random phase fluctuations in the probing signal generated by the vibrator.


      PubDate: 2012-12-15T09:27:58Z
       
  • Author Index
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40




      PubDate: 2012-12-15T09:27:58Z
       
  • Subject Index
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 40




      PubDate: 2012-12-15T09:27:58Z
       
  • Copyright
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 39




      PubDate: 2012-12-15T09:27:58Z
       
  • Contents
    • Abstract: 2010
      Publication year: 2010
      Source:Handbook of Geophysical Exploration: Seismic Exploration, Volume 39




      PubDate: 2012-12-15T09:27:58Z
       
 
 
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