scholarly journals Fault low velocity zones deduced by trapped waves and their relation to earthquake rupture processes

2002 ◽  
Vol 54 (11) ◽  
pp. 1045-1048 ◽  
Author(s):  
Yasuto Kuwahara ◽  
Hisao Ito
Keyword(s):  
Earthquake Rupture ◽  
Trapped Waves ◽  
Low Velocity ◽  
Earthquake Rupture Processes

Low-velocity damaged structure of the San Andreas Fault at Parkfield from fault zone trapped waves

2004 ◽  
Vol 31 (12) ◽  
pp. n/a-n/a ◽  
Author(s):  
Yong-Gang Li ◽  
John E. Vidale ◽  
Elizabeth S. Cochran
Keyword(s):  
Fault Zone ◽  
San Andreas Fault ◽  
Trapped Waves ◽  
Low Velocity ◽  
San Andreas

scholarly journals A stochastic rupture earthquake code based on the fiber bundle model (TREMOL v0.1): application to Mexican subduction earthquakes

2019 ◽  
Vol 12 (5) ◽  
pp. 1809-1831 ◽  
Author(s):  
Marisol Monterrubio-Velasco ◽  
Quetzalcóatl Rodríguez-Pérez ◽  
Ramón Zúñiga ◽  
Doreen Scholz ◽  
Armando Aguilar-Meléndez ◽  
...  
Keyword(s):  
Fiber Bundle ◽  
Fault Plane ◽  
Heterogeneous Material ◽  
Computer Code ◽  
Rupture Process ◽  
Maximum Magnitude ◽  
Earthquake Rupture ◽  
General Terms ◽  
Fiber Bundle Model ◽  
Earthquake Rupture Processes

Abstract. In general terms, earthquakes are the result of brittle failure within the heterogeneous crust of the Earth. However, the rupture process of a heterogeneous material is a complex physical problem that is difficult to model deterministically due to numerous parameters and physical conditions, which are largely unknown. Considering the variability within the parameterization, it is necessary to analyze earthquakes by means of different approaches. Computational physics may offer alternative ways to study brittle rock failure by generating synthetic seismic data based on physical and statistical models and through the use of only few free parameters. The fiber bundle model (FBM) is a stochastic discrete model of material failure, which is able to describe complex rupture processes in heterogeneous materials. In this article, we present a computer code called the stochasTic Rupture Earthquake MOdeL, TREMOL. This code is based on the principle of the FBM to investigate the rupture process of asperities on the earthquake rupture surface. In order to validate TREMOL, we carried out a parametric study to identify the best parameter configuration while minimizing computational efforts. As test cases, we applied the final configuration to 10 Mexican subduction zone earthquakes in order to compare the synthetic results by TREMOL with seismological observations. According to our results, TREMOL is able to model the rupture of an asperity that is essentially defined by two basic dimensions: (1) the size of the fault plane and (2) the size of the maximum asperity within the fault plane. Based on these data and few additional parameters, TREMOL is able to generate numerous earthquakes as well as a maximum magnitude for different scenarios within a reasonable error range. The simulated earthquake magnitudes are of the same order as the real earthquakes. Thus, TREMOL can be used to analyze the behavior of a single asperity or a group of asperities since TREMOL considers the maximum magnitude occurring on a fault plane as a function of the size of the asperity. TREMOL is a simple and flexible model that allows its users to investigate the role of the initial stress configuration and the dimensions and material properties of seismic asperities. Although various assumptions and simplifications are included in the model, we show that TREMOL can be a powerful tool to deliver promising new insights into earthquake rupture processes.

Fault zone trapped seismic waves

1990 ◽  
Vol 80 (5) ◽  
pp. 1245-1271 ◽  
Author(s):  
Y.-G. Li ◽  
P. C. Leary
Keyword(s):  
Fault Zone ◽  
Seismic Waves ◽  
Fault Plane ◽  
Body Wave ◽  
Velocity Model ◽  
Trapped Waves ◽  
Low Velocity ◽  
Near Surface ◽  
San Andreas ◽  
Borehole Seismic

Abstract Two instances of fault zone trapped seismic waves have been observed. At an active normal fault in crystalline rock near Oroville in northern California, trapped waves were excited with a surface source and recorded at five near-fault borehole depths with an oriented three-component borehole seismic sonde. At Parkfield, California, a borehole seismometer at Middle Mountain recorded at least two instances of the fundamental and first higher mode seismic waves of the San Andreas fault zone. At Oroville recorded particle motions indicate the presence of both Love and Rayleigh normal modes. The Love-wave dispersion relation derived for an idealized wave guide with velocity structure determined by body-wave travel-time inversion yields seismograms of the fundamental mode that are consistent with the observed Love-wave amplitude and frequency. Applying a similar velocity model to the Parkfield observations, we obtain a good fit to the trapped wavefield amplitude, frequency, dispersion, and mode time separation for an asymmetric San Andreas fault zone structure—a high-velocity half-space to the southwest, a low-velocity fault zone, a transition zone containing the borehole seismometer, and an intermediate velocity half-space to the northeast. In the Parkfield borehole seismic data set, the locations (depth and offset normal to fault plane) of natural seismic events which do or do not excite trapped waves are roughly consistent with our model of the low velocity zone. We conclude that it is feasible to obtain near-surface borehole records of fault zone trapped waves. Because trapped modes are excited only by events close to the fault zone proper—thereby fixing these events in space relative to the fault—a wider investigation of possible trapped mode waveforms recorded by a borehole seismic network could lead to a much refined body-wave/tomographic velocity model of the fault and to a weighting of events as a function of offset from the fault plane. It is an open question whether near-surface sensors exist in a stable enough seismic environment to use trapped modes as an earth monitoring device.

scholarly journals Paleoseismological uncertainty estimation in the Acambay region, Central Mexico

2017 ◽  
Vol 56 (3) ◽  
Author(s):  
Quetzalcoatl Rodríguez-Pérez ◽  
F. Ramón Zúñiga ◽  
Pierre Lacan
Keyword(s):  
Seismic Hazard ◽  
Hazard Analysis ◽  
Central Mexico ◽  
Earthquake Rupture ◽  
Relative Importance ◽  
Logic Tree ◽  
Systematic Treatment ◽  
Recurrence Period ◽  
Geological Features ◽  
Earthquake Rupture Processes

Paleseismological studies provide valuable information of the earthquake rupture processes such as fault dimensions, average and maximum displacements, as well as recurrence times and magnitudes of events which took place in the geologic past. This information is based on observations of the geological record. Interpretation of geological observa-tions has a source of uncertainties inherent to the large number of hypothesis that explain the observed geological features. Information obtained from paleoseismic studies is im-portant in seismic hazard analyses, and particularly crucial for regions of low seismic activity where the recurrence period of major earthquakes reaches several thousand years. However, using this information in hazard analysis requires the systematic treatment of uncertainties. We estimated uncertainties of four paleoseismological studies conducted at three different faults of the Acambay graben region in Central Mexico. The method used is based on a logic-tree formalism that quantifies the cumulative uncertainties associated with the different stages of the paleoseismic studies together with a quantification of the entropy at each step and at the end of the process. The final uncertainty and its relative importance in seismic hazard analysis is expressed as the paleoseismic quality factor, which indicate 0.14, 0.40-0.50, and 0.41 for the Acambay-Tixmadejé, Pastores and San Mateo faults, respectively. These values can be incorporated in seismic hazard analyses for the region.

scholarly journals Petrophysical, geochemical, and hydrological evidence for extensive fracture-mediated fluid and heat transport in the Alpine Fault's hanging-wall damage zone

2021 ◽  
Author(s):  
John Townend ◽  
Rupert Sutherland ◽  
VG Toy ◽  
ML Doan ◽  
B Célérier ◽  
...  
Keyword(s):  
Numerical Models ◽  
Hanging Wall ◽  
Damage Zone ◽  
Active Faults ◽  
Outer Zone ◽  
Earthquake Rupture ◽  
Fault Rock ◽  
Spatial And Temporal Scales ◽  
Alpine Fault ◽  
Earthquake Rupture Processes

© 2017. American Geophysical Union. All Rights Reserved. Fault rock assemblages reflect interaction between deformation, stress, temperature, fluid, and chemical regimes on distinct spatial and temporal scales at various positions in the crust. Here we interpret measurements made in the hanging-wall of the Alpine Fault during the second stage of the Deep Fault Drilling Project (DFDP-2). We present observational evidence for extensive fracturing and high hanging-wall hydraulic conductivity (∼10−9 to 10−7 m/s, corresponding to permeability of ∼10−16 to 10−14 m2) extending several hundred meters from the fault's principal slip zone. Mud losses, gas chemistry anomalies, and petrophysical data indicate that a subset of fractures intersected by the borehole are capable of transmitting fluid volumes of several cubic meters on time scales of hours. DFDP-2 observations and other data suggest that this hydrogeologically active portion of the fault zone in the hanging-wall is several kilometers wide in the uppermost crust. This finding is consistent with numerical models of earthquake rupture and off-fault damage. We conclude that the mechanically and hydrogeologically active part of the Alpine Fault is a more dynamic and extensive feature than commonly described in models based on exhumed faults. We propose that the hydrogeologically active damage zone of the Alpine Fault and other large active faults in areas of high topographic relief can be subdivided into an inner zone in which damage is controlled principally by earthquake rupture processes and an outer zone in which damage reflects coseismic shaking, strain accumulation and release on interseismic timescales, and inherited fracturing related to exhumation.

Imaging fine seismic structures of faults with fault-zone trapped waves

2020 ◽  
Author(s):  
Hui Su ◽  
Yuanze Zhou
Keyword(s):  
Fault Zone ◽  
Earthquake Prediction ◽  
Transport Theory ◽  
Damage Zone ◽  
Fault Zones ◽  
Physical Parameters ◽  
Trapped Waves ◽  
Low Velocity ◽  
Velocity Models ◽  
Before And After

<p>A fault is a low-velocity zone with widely distributed scatterers compared to the surrounding uniform materials because of the highly damaged rocks in its core. When seismic waves travel through faults, they will reflect on boundaries multiply and be trapped in the fault zones which cause the energy redistribution and generate coda waves with complicated characteristics after the direct P- and S- waves. The coda is named fault-zone trapped waves (FZTWs) (Li et al., 1990). The amplitude and duration characteristics of FZTWs (Li et al., 2016) can be used to constrain the geometric features of the fault and the physical parameters of the scatterers, so the fine structure of the fault can be finally obtained. We observed some FZTWs at several Hi-net stations in Japan, which were generated by low magnitude aftershocks following large earthquakes. Relatively strong FZTWs can be recorded by the seismic stations near or on the fault where the events happened. In this study, we simulate the theoretic envelops of FZTWs with radiative transport theory (Sanborn et al., 2017) for possible velocity models with scatterers described with von Karman distribution (Sato et al., 2012). While the theoretical envelops of FZTWs fit the observed ones well,  the fine fault model is determined. The FZTWs from different events before and after the main shock can be used to determine the physical properties of faults and their adjoint area varied in the seismogenic process, then we can deeply understand the fault evolutions before and after earthquakes. The varying properties of faults can provide a new perspective for earthquake preparation and a new reference for earthquake prediction and promotes the development of earthquake prediction.<br>Li, Y. G., R. D. Catchings, and M. R. Goldman. 2016, Subsurface Fault Damage Zone of the 2014Mw 6.0 South Napa, California, Earthquake Viewed from Fault‐Zone Trapped Waves. Bulletin of the Seismological Society of America, 106, no. 6,2747-2763. doi: 10.1785/0120160039.<br>Li, Y. G., P. Leary, K. Aki, and P. Malin. 1990, Seismic Trapped Modes in the Oroville and San-Andreas Fault Zones. Science, 249, no. 4970,763-766. doi: 10.1126/science.249.4970.763.<br>Sanborn, C. J., V. F. Cormier, and M. Fitzpatrick. 2017, Combined Effects of Deterministic and Statistical Structure on High-frequency Regional Seismograms. Geophysical Journal International, 210, no. 2,1143-1159. doi: 10.1093/gji/ggx219.<br>Sato H., Fehler M.C. 2012, Seismic Wave Propagation and Scattering in the Heterogeneous Earth, 2nd edn, Springer-Verlag.</p>

Rupture Branching Structure of the 2014 Mw 6.0 South Napa, California, Earthquake Inferred from Explosion‐Generated Fault‐Zone Trapped Waves

2019 ◽  
Vol 109 (5) ◽  
pp. 1907-1921
Author(s):  
Yong‐Gang Li ◽  
Rufus D. Catchings ◽  
Mark R. Goldman
Keyword(s):  
Fault Zone ◽  
Rupture Zone ◽  
Seismic Velocities ◽  
Trapped Waves ◽  
Low Velocity ◽  
Surface Rupture ◽  
Multiple Fault ◽  
S Waves ◽  
Surface Rupture Zone ◽  
Surface Ruptures

Abstract We present evidence for multiple fault branches of the West Napa fault zone (WNFZ) based on fault‐zone trapped waves (FZTWs) generated by two explosions that were detonated within the main surface rupture zone produced by the 24 August 2014 Mw 6.0 South Napa earthquake. The FZTWs were recorded by a 15‐kilometer‐long dense (100 m spacing) linear seismic array consisting of 155 4.5‐hertz three‐component seismometers that were deployed across the surface ruptures and adjacent faults in Napa Valley in the summer of 2016. The two explosions were located ∼3.5  km north and ∼5  km south of the 2016 recording array. Prominent FZTWs, with large amplitudes and long wavetrains following the P and S waves, are observed on the seismograms. We analyzed FZTW waveforms in both time and frequency domains to characterize the branching structure of subsurface rupture zones along the WNFZ. The 2014 surface rupture zone was ∼12  km in length along the main trace of the WNFZ, which appears to form an ∼400–600‐meter‐wide low‐velocity waveguide to depths in excess of 5–7 km. Seismic velocities within the main rupture are reduced by 40%–50% relative to the surrounding‐rock velocities. Within 1.5 km of the main trace of the WNFZ, there are at least two subordinate fault traces that formed 3‐ to 6‐kilometer‐long surface breaks during the 2014 mainshock. Our modeling suggests that these subordinate fault traces are also low‐velocity waveguides that connect with the main rupture at depths of ∼2–3  km, forming a flower structure. FZTWs were also recorded at seismic stations across the Carneros fault (CF), which is ∼1  km west of the WNFZ; this suggests that the CF connects with the WNFZ at shallow depths, even though the CF did not experience surface rupture during the 2014 Mw 6.0 mainshock. 3D finite‐difference simulations of recorded FZTWs imply a branching structure along multiple fault strands associated with the WNFZ.

scholarly journals Low-Velocity Damage Zone on the San Andreas Fault at Depth near SAFOD Site at Parkfield Delineated by Fault-Zone Trapped Waves

2007 ◽  
Vol SpecialIssue ◽  
pp. 73-77 ◽  
Author(s):  
Y.-G. Li ◽  
P. E. Malin ◽  
J. E. Vidal
Keyword(s):  
Fault Zone ◽  
San Andreas Fault ◽  
Damage Zone ◽  
Trapped Waves ◽  
Low Velocity ◽  
San Andreas

No abstract available. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.s01.09.2007" target="_blank">10.2204/iodp.sd.s01.09.2007</a>

The Multiscale Structure of the Longmen Shan Central Fault Zone from Local and Teleseismic Data Recorded by Short-Period Dense Arrays

2020 ◽  
Vol 110 (6) ◽  
pp. 3077-3087
Author(s):  
Yafen Huang ◽  
Hongyi Li ◽  
Xin Liu ◽  
Yuting Zhang ◽  
Min Liu ◽  
...  
Keyword(s):  
Fault Zone ◽  
Receiver Functions ◽  
Seismic Array ◽  
Trapped Waves ◽  
Low Velocity ◽  
Surface Rupture ◽  
P Waves ◽  
Low Velocity Zone ◽  
Short Period ◽  
Velocity Zone

ABSTRACT The Longmen Shan fault zone (FZ), which consists of the back-range, the central, and the front-range faults, acts as the boundary between the Sichuan basin and eastern Tibet. In this study, local and teleseismic waveforms recorded by a 2D small aperture seismic array (176 temporary short-period seismometers) deployed by China University of Geosciences (Beijing) from 22 October to 20 November 2017 and a dense linear seismic array of 16 stations deployed by Geophysical Exploration Center, China Earthquake Administration during July 2008 are used to study the FZ structure by analyzing FZ-trapped waves (FZTWs), the radial-to-vertical amplitude ratio, and travel-time delays. Based on power density spectra analysis, FZTWs from local events with larger amplitudes and longer wavetrains are clearly observed at stations 6002–6003, 6013–6025, and W025–W032. The dispersion measured from trapped waves is quite weak. The near-surface shear velocity structure estimated from the radial-to-vertical amplitude ratios of local initial P waves shows a low-velocity zone around the surface rupture trace. The slight time delay of direct P waves examined from local and teleseismic events indicates a relatively shallow slow structure beneath the arrays. Through the comprehensive analysis of the central FZ, our results suggest a shallow low-velocity zone with a width of ∼150–160  m along the surface rupture trace. Moreover, our P-wave receiver functions reveal that the Moho depth beneath the Longmen Shan FZ is approximately 45 km, and receiver functions at stations located within the surface rupture zone show more complicated waveforms than those off the surface rupture.

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