Properties of seismic fault zone waves and their utility for imaging low-velocity structures

Three-dimensional P wave velocity models under the Zipingpu reservoir in Longmenshan fault zone are obtained with a resolution of 2 km in the horizontal direction and 1 km in depth. We used a total of 8589 P wave arrival times from 1014 local earthquakes recorded by both the Zipingpu reservoir network and temporary stations deployed in the area. The 3-D velocity images at shallow depth show the low-velocity regions have strong correlation with the surface trace of the Zipingpu reservoir. According to the extension of those low-velocity regions, the infiltration depth directly from the Zipingpu reservoir itself is limited to 3.5 km depth, while the infiltration depth downwards along the Beichuan-Yingxiu fault in the study area is about 5.5 km depth. Results show the low-velocity region in the east part of the study area is related to the Proterozoic sedimentary rocks. The Guanxian-Anxian fault is well delineated by obvious velocity contrast and may mark the border between the Tibetan Plateau in the west and the Sichuan basin in the east.

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

Geophysical Research Letters ◽

10.1029/2003gl019044 ◽

2004 ◽

Vol 31 (12) ◽

pp. n/a-n/a ◽

Cited By ~ 61

Author(s):

Yong-Gang Li ◽

John E. Vidale ◽

Elizabeth S. Cochran

Keyword(s):

Fault Zone ◽

San Andreas Fault ◽

Trapped Waves ◽

Low Velocity ◽

San Andreas

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Fault Zone Guided Wave generation on the locked, late interseismic Alpine Fault, New Zealand

10.26686/wgtn.13818791.v1 ◽

2021 ◽

Author(s):

JD Eccles ◽

AK Gulley ◽

PE Malin ◽

CM Boese ◽

John Townend ◽

...

Keyword(s):

Fault Zone ◽

Plate Boundary ◽

Guided Wave ◽

S Wave ◽

Low Velocity ◽

Catchment Scale ◽

Near Surface ◽

Low Velocity Zone ◽

Alpine Fault ◽

Velocity Zone

© 2015. American Geophysical Union. All Rights Reserved. Fault Zone Guided Waves (FZGWs) have been observed for the first time within New Zealand's transpressional continental plate boundary, the Alpine Fault, which is late in its typical seismic cycle. Ongoing study of these phases provides the opportunity to monitor interseismic conditions in the fault zone. Distinctive dispersive seismic codas (~7-35Hz) have been recorded on shallow borehole seismometers installed within 20m of the principal slip zone. Near the central Alpine Fault, known for low background seismicity, FZGW-generating microseismic events are located beyond the catchment-scale partitioning of the fault indicating lateral connectivity of the low-velocity zone immediately below the near-surface segmentation. Initial modeling of the low-velocity zone indicates a waveguide width of 60-200m with a 10-40% reduction in S wave velocity, similar to that inferred for the fault core of other mature plate boundary faults such as the San Andreas and North Anatolian Faults.

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Numerical modelling technique for predicting the seismic fault zone (SFZ) in the earthquakes affected area, NW Himalayas with its neotectonic implication

Journal of Life and Earth Science ◽

10.3329/jles.v2i2.7499 ◽

1970 ◽

Vol 2 (2) ◽

pp. 57-65

Author(s):

M Farhad Howladar ◽

Sharmin Afroz ◽

Shofiqul Islam

Keyword(s):

Fault Zone ◽

Numerical Technique ◽

Strain Analysis ◽

Normal Fault ◽

Focal Mechanism Solution ◽

Mathematical Form ◽

Finite Elements Analysis ◽

Nw Himalaya ◽

Potential Region ◽

Seismic Fault

Finite elements analysis is a powerful tool, often used for analyzing problems on stress, that can be successfully employed to analyze the finite deformation of geological structures in a mathematical form on a digital computer. Over the last century, great earthquakes with magnitudes of 7->8 have struck in the NW Himalaya; the 1905 Kangra earthquake is one of them. This study performed a plane strain analysis of failure stress and faults in these earthquakes potential region based on the seismic geologic cross profile employing the two-dimensional finite element method under elastic material state with Mohr Coulomb failure criterion. The results show that the normal fault initiates at deeper level, whereas with increasing convergent displacement the thrust fault appears in the shallower region. The results of the simulation are compared with the available seismic and earthquakes focal mechanism solution data of the area which shows the close similarities between the distribution of simulated fault and microseismicity in the deeper region of Chamba Nappe (CN) and along the upper part of the Mid Crustal Ramp (MCR) which might be the Seismic Fault Zone (SFZ) of the region. Moreover, the intense localization of faults along the frontal part of the model indicates that this part is active in nature at present, which is responsible for the neotectonics in the Himalayas. Keywords: NW Himalaya; numerical technique; seismic fault zone; neotectonics DOI: 10.3329/jles.v2i2.7499 J. Life Earth Sci., Vol. 2(2) 57-65, 2007

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Response Analysis of Bridge across Seismic Fault Zone

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.178-181.2224 ◽

2012 ◽

Vol 178-181 ◽

pp. 2224-2227

Author(s):

Qi Zhen Li ◽

Hong Quan Li ◽

Zhi Qian Zhang

Keyword(s):

Fault Zone ◽

Bridge Pier ◽

Additional Stress ◽

Response Analysis ◽

Geological Condition ◽

Structure Model ◽

Bridge Structure ◽

Continuous Beam ◽

Seismic Fault ◽

Deformation Law

Through simulating the happening location of the fault zone, the structure model is duly simplified, analysing the forced deformation law of the bridge surface with different fault zone position. Because of statically indeterminate structure, continuous beam shall be produced larger additional moment, shear force and torque as a result of displacement in bridge pier, additional stress will be increased with the the increasement of fault zone displacement, especially for the top surface parts of bridge pier. Hence, the corresponding position of the structure and construction measures for reinforcement should strengthened, the overall rigidity of the structure should be improved, and based on the study of the bridge across the fault zone is a simplified, and the actual stress process may be more complex, the investigation on geological condition must be clear, and avoid the bridge structure crossing fault zone.

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