Earthquake relocation and 3-dimensional crustal structure of P-wave velocity in cen-tral-western China

2004 ◽  
Vol 17 (1) ◽  
pp. 20-30 ◽  
Author(s):  
Zhi-xian Yang ◽  
Xiang-wei Yu ◽  
Yue-jun Zheng ◽  
Yun-tai Chen ◽  
Xiao-xi Ni ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Crustal Structure ◽  
P Wave ◽  
Western China ◽  
Earthquake Relocation ◽  
3 Dimensional ◽  
P Wave Velocity

Crustal structure across the Nain – Makkovik boundary on the continental shelf off Labrador from seismic refraction data

1996 ◽  
Vol 33 (3) ◽  
pp. 460-471 ◽  
Author(s):  
Ian Reid
Keyword(s):  
Continental Shelf ◽  
Wave Velocity ◽  
Crustal Structure ◽  
Lower Crust ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Seismic Refraction ◽  
P Wave ◽  
Air Gun ◽  
P Wave Velocity

A detailed seismic refraction profile was shot along the continental shelf off Labrador, across the boundary between the Archean Nain Province to the north and the Proterozoic Makkovik orogenic zone to the south. A large air-gun source was used, with five ocean-bottom seismometers as receivers. The data were analysed by forward modelling of traveltimes and amplitudes and provided a well-determined seismic velocity structure of the crust along the profile. Within the Nain province, thin postrift sediments are underlain by crust with a P-wave velocity of 6.1 km/s, which increases with depth and reaches 6.6 km/s at about 8 km. Moho is at around 28 km, and there is no evidence for a high-velocity (>7 km/s) lower crust. The P- and S-wave velocity structure is consistent with a gneissic composition for the Archean upper crust, and with granulites becoming gradually more mafic with depth for the intermediate and lower crust. In the Makkovik zone, the sediments are thicker, and a basement layer of P-wave velocity 5.5–5.7 km/s is present, probably due to reworking of the crust and the presence of Early Proterozoic volcanics and metasediments. Upper crustal velocities are lower than in the Nain Province. The crustal thickness, at 23 km, is less, possibly due in part to greater crustal stretching during the Mesozoic rifting of the Labrador Sea. The crustal structure across the Nain–Makkovik boundary is similar to that across the corresponding Archean–Ketilidian boundary off southwest Greenland.

scholarly journals Geophysical and analytical determination of overstressed zones in exploited coal seam: a case study

2021 ◽  
Author(s):  
Dariusz Chlebowski ◽  
Zbigniew Burtan
Keyword(s):  
Coal Seam ◽  
Wave Velocity ◽  
Seismic Tomography ◽  
Analytical Modeling ◽  
Coal Mines ◽  
Vertical Stress ◽  
P Wave ◽  
Rockburst Hazard ◽  
State Of Stress ◽  
P Wave Velocity

AbstractA variety of geophysical methods and analytical modeling are applied to determine the rockburst hazard in Polish coal mines. In particularly unfavorable local conditions, seismic profiling, active/passive seismic tomography, as well as analytical state of stress calculating methods are recommended. They are helpful in verifying the reliability of rockburst hazard forecasts. In the article, the combined analysis of the state of stress determined by active seismic tomography and analytical modeling was conducted taking into account the relationship between the location of stress concentration zones and the level of rockburst hazard. A longwall panel in the coal seam 501 at a depth of ca.700 m in one of the hard coal mines operating in the Upper Silesian Coal Basin was a subject of the analysis. The seismic tomography was applied for the reconstruction of P-wave velocity fields. The analytical modeling was used to calculate the vertical stress states basing on classical solutions offered by rock mechanics. The variability of the P-wave velocity field and location of seismic anomaly in the coal seam in relation to the calculated vertical stress field arising in the mined coal seam served to assess of rockburst hazard. The applied methods partially proved their adequacy in practical applications, providing valuable information on the design and performance of mining operations.

Crustal P-wave velocity structure and earthquake distribution in the Jiaodong Peninsula, China

2021 ◽  
pp. 228973
Author(s):  
Junhao Qu ◽  
Stephen S. Gao ◽  
Changzai Wang ◽  
Kelly H. Liu ◽  
Shaohui Zhou ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Velocity Structure ◽  
P Wave ◽  
Jiaodong Peninsula ◽  
P Wave Velocity ◽  
Earthquake Distribution ◽  
P Wave Velocity Structure
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