Frequency band-dependence of S-wave splitting in China mainland and its implications

2001 ◽  
Vol 44 (7) ◽  
pp. 659-665 ◽  
Author(s):  
Kun Liu ◽  
Zhongjie Zhang ◽  
Jiafu Hu ◽  
Jiwen Teng
Keyword(s):  
Frequency Band ◽  
S Wave ◽  
Wave Splitting ◽  
China Mainland

Frequency-dependent S-wave splitting parameters analysis: A case study from azimuthal PS data, Sanhu area of the Qaidam Basin, China

Geophysics ◽  
2019 ◽  
Vol 84 (6) ◽  
pp. B375-B386
Author(s):  
Yun Wang ◽  
Chao Wang ◽  
Jianfeng Li ◽  
Yuanyuan Yue
Keyword(s):  
Frequency Band ◽  
Delay Time ◽  
Large Scale ◽  
Qaidam Basin ◽  
Dominant Frequency ◽  
S Wave ◽  
Frequency Dependent ◽  
Fracture Orientation ◽  
Fracture Systems ◽  
Wave Splitting

The Sanhu area, which is located in the eastern Qaidam Basin in China and formed of low-amplitude anticlinal and lithologic traps, is a favorable area for biogas exploration. The fracture systems in this area are characterized in detail with the use of frequency-dependent S-wave splitting parameters, which are sensitive to the size of the fractures. The results indicate that the delay time between slow and fast S-waves decreases rapidly with increasing frequency between 5 and 30 Hz, and then it slowly decreases to a stationary value at high frequencies. Moreover, the frequency-dependent delay times suggest that fractures of different scale have different 2D density distribution. The frequency-dependent orientation of the fractures suggests that large-scale fractures, which correspond to a low-frequency band (5–11 Hz), are oriented at approximately N48°E and have small random disturbances. The mesoscale fractures that correspond to the dominant frequency band (12–36 Hz) are oriented along approximately N54°E in the northeastern region and N45°E over the remaining area. As expected, the average fracture orientation and delay time of the dominant frequency band are consistent with previous results from conventional S-wave splitting analysis in the time domain, but the frequency-dependent fracture orientation and delay time indicate finer heterogeneity and spatial anomalies. In summary, the results show the potential for accurately characterizing fracture systems using frequency-dependent S-wave splitting parameters.

Guangxi Longtan Reservoir Earthquakes S-Wave Splitting

2017 ◽  
pp. 477-493
Author(s):  
Lijuan Lu ◽  
Bin Zhou ◽  
Xiang Wen ◽  
Shuiping Shi ◽  
Chunheng Yan ◽  
...  
Keyword(s):  
S Wave ◽  
Wave Splitting ◽  
Longtan Reservoir

The 1998 Valhall microseismic data set: An integrated study of relocated sources, seismic multiplets, and S-wave splitting

Geophysics ◽  
2009 ◽  
Vol 74 (5) ◽  
pp. B183-B195 ◽  
Author(s):  
K. De Meersman ◽  
J.-M. Kendall ◽  
M. van der Baan
Keyword(s):  
Seismic Anisotropy ◽  
Amplitude Ratio ◽  
Temporal Variations ◽  
Oil Field ◽  
P Wave ◽  
Wave Form ◽  
S Wave ◽  
Data Set ◽  
Wave Splitting ◽  
Source Mechanisms

We relocate 303 microseismic events recorded in 1998 by sensors in a single borehole in the North Sea Valhall oil field. A semiautomated array analysis method repicks the P- and S-wave arrival times and P-wave polarizations, which are needed to locate these events. The relocated sources are confined predominantly to a [Formula: see text]-thick zone just above the reservoir, and location uncertainties are half those of previous efforts. Multiplet analysis identifies 40 multiplet groups, which include 208 of the 303 events. The largest group contains 24 events, and five groups contain 10 or more events. Within each multiplet group, we further improve arrival-time picking through crosscorrelation, which enhances the relative accuracy of the relocated events and reveals that more than 99% of the seismic activity lies spatially in three distinct clusters. The spatial distribution of events and wave-form similarities reveal two faultlike structures that match well with north-northwest–south-southeast-trending fault planes interpreted from 3D surface seismic data. Most waveform differences between multiplet groups located on these faults can be attributed to S-wave phase content and polarity or P-to-S amplitude ratio. The range in P-to-S amplitude ratios observed on the faults is explained best in terms of varying source mechanisms. We also find a correlation between multiplet groups and temporal variations in seismic anisotropy, as revealed by S-wave splitting analysis. We explain these findings in the context of a cyclic recharge and dissipation of cap-rock stresses in response to production-driven compaction of the underlying oil reservoir. The cyclic nature of this mechanism drives the short-term variations in seismic anisotropy and the reactivation of microseismic source mechanisms over time.

scholarly journals Diurnal expansion and contraction of englacial fracture networks revealed by seismic shear wave splitting

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Wojciech Gajek ◽  
Dominik Gräff ◽  
Sebastian Hellmann ◽  
Alan W. Rempel ◽  
Fabian Walter
Keyword(s):  
Shear Wave ◽  
Large Scale ◽  
Elastic Anisotropy ◽  
Shear Wave Splitting ◽  
Subsurface Water ◽  
Water Drainage ◽  
Fracture Networks ◽  
S Wave ◽  
Alpine Glacier ◽  
Wave Splitting

AbstractFractures contribute to bulk elastic anisotropy of many materials in the Earth. This includes glaciers and ice sheets, whose fracture state controls the routing of water to the base and thus large-scale ice flow. Here we use anisotropy-induced shear wave splitting to characterize ice structure and probe subsurface water drainage beneath a seismometer network on an Alpine glacier. Shear wave splitting observations reveal diurnal variations in S-wave anisotropy up to 3%. Our modelling shows that when elevated by surface melt, subglacial water pressures induce englacial hydrofractures whose volume amounts to 1-2 percent of the probed ice mass. While subglacial water pressures decrease, these fractures close and no fracture-induced anisotropy variations are observed in the absence of meltwater. Consequently, fracture networks, which are known to dominate englacial water drainage, are highly dynamic and change their volumes by 90-180 % over subdaily time scales.

Determination of S-wave Site Response in Anchorage, Alaska in the 1-9 Hz Frequency Band

2002 ◽  
Vol 159 (11-12) ◽  
pp. 2673-2698 ◽  
Author(s):  
S. K. Nath ◽  
N. N. Biswas ◽  
M. Dravinski ◽  
A. S. Papageorgiou
Keyword(s):  
Frequency Band ◽  
Site Response ◽  
S Wave
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