An attempt to detect temporal variations of crustal structure in the source area of the 2006 Wen-An earthquake in North China

Lei, Jianshe; Zhao, Dapeng; Xie, Furen; Liu, Jie

doi:10.1016/j.jseaes.2010.07.003

Cited by 10 publications

(8 citation statements)

References 42 publications

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“…When the fluids enter the active faults, the effective normal stress across the fault planes would decrease and thus faulting could be triggered to generate these large earthquakes in the Tien Shan region. A similar structure is also found in the source areas of the 1605 Qiongshan earthquake ( M 7.5) in southernmost China [ Lei et al , 2009a], the 1976 Tangshan earthquake ( M 7.8) and 2006 Wen‐An earthquake ( M 5.1) in North China [ Huang and Zhao , 2004; Lei et al , 2008, 2011], the 1995 Kobe earthquake ( M 7.2) in Japan [ Zhao et al , 1996], the 2001 Bhuj earthquake ( M 7.6) in India [ Mishra and Zhao , 2003], and the 2008 Wenchuan earthquake ( M 8.0) in southwestern China [ Lei and Zhao , 2009]. …”

Section: Discussionsupporting

confidence: 64%

Seismic tomographic imaging of the crust and upper mantle under the central and western Tien Shan orogenic belt

Lei¹

2011

J. Geophys. Res.

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[1] Detailed 3-D tomographic images of P and S wave velocity (Vp, Vs) and Poisson's ratio (s) under the central and western Tien Shan orogenic belt are determined by using a large number of high-quality P and S wave arrival times from local earthquakes. The results show that under the Tien Shan orogenic belt high-Vp, high-Vs, and low-s anomalies are revealed in the upper and middle crust, possibly indicating the existence of the Paleozoic crystalline basement rocks, while low-Vp, low-Vs, and high-s anomalies appear in the lower crust and upper mantle, perhaps suggesting that the hot and wet material is upwelling under the Tien Shan orogenic belt from the mantle. Some high-Vp, high-Vs, and low-s anomalies are tilted toward the Tien Shan along with the seismicity. These are found in the collision zones between the Tien Shan and the Tarim basin in the south and the Kazakh shield in the north and suggest the underthrusting of the Tarim and Kazakh lithosphere beneath the Tien Shan. Meanwhile, some low-Vp, low-Vs, and high-s anomalies are imaged in other parts of these collision zones, perhaps indicating the intrusion of the hot and wet material into the crust from the upper mantle. These results indicate that both the upwelling of the hot and wet material and the underthrusting of the Tarim and Kazakh lithosphere may have played an important role in the mountain building. Under the Tarim and Fergana basins, low-Vp, low-Vs, and high-s anomalies are revealed in the upper crust, while high-Vp, high-Vs, and low-s anomalies are visible in the lower crust and upper mantle. These may reflect the existence of less compacted sedimentary material in the shallow crust and more highly compacted craton-like structures in the deeper crust and upper mantle under the basins. The Talas-Fergana fault shows an obvious tectonic boundary between central and western Tien Shan. The central Tien Shan displays high-Vp, high-Vs, and low-s anomalies in the upper and middle crust, while western Tien Shan exhibits low-Vp, low-Vs, and high-s anomalies. However, the pattern of seismic structure between central and western Tien Shan reverses in the lower crust. Such a correlation may extend down to the upper mantle, suggesting that the Talas-Fergana fault may be a lithospheric-scale boundary. Additionally, a columnar low-Vp and low-Vs anomaly is clearly observed around the turning point of the Talas-Fergana fault from the NWN to NWW trending orientations and may indicate that the fault provides a channel for the hot and wet material upwelling from the mantle to the surface.

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Section: Discussionsupporting

confidence: 64%

Seismic tomographic imaging of the crust and upper mantle under the central and western Tien Shan orogenic belt

Lei¹

2011

J. Geophys. Res.

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“…The use of multiple reflected waves in the crust (SmS, sSmS) results in a high-resolution crustal tomography with only two stations . The use of Moho reflected waves (PmP) in tomography leads to a better mapping of the lower crustal structure and the crustal thickness (e.g., Salah and Zhao, 2004;Xia et al, 2007;Sun et al, 2008;Gupta et al, 2009b;Lei et al, 2011). The addition of various types of later phases in the mantle and core in global tomography enables a better imaging of deep mantle plumes (Zhao, 2001c(Zhao, , 2007(Zhao, , 2009.…”

Section: Discussion and Future Perspectivesmentioning

confidence: 99%

“…Some researchers have tried to determine temporal variations in structure (i.e., 4-D tomography). Examples are the study of geothermal reservoir changes at The Geysers, CA (Gunasekera et al, 2003), the investigation of temporal changes at Mammoth Mountain, CA, related to CO 2 outgassing Julian and Foulger, 2010), and the source area of a large earthquake (e.g., Lei et al, 2011). But one should be very careful in 4-D tomography studies that the data sets used for the different time periods should be the same in order to detect the temporal variations in the 3-D structure.…”

Section: Discussion and Future Perspectivesmentioning

confidence: 99%

Tomography and Dynamics of Western-Pacific Subduction Zones

Zhao¹

2012

Monogr. Environ. Earth Planets

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We review the significant recent results of multiscale seismic tomography of the Western-Pacific subduction zones and discuss their implications for seismotectonics, magmatism, and subduction dynamics, with an emphasis on the Japan Islands. Many important new findings are obtained due to technical advances in tomography, such as the handling of complex-shaped velocity discontinuities, the use of various later phases, the joint inversion of local and teleseismic data, tomographic imaging outside a seismic network, and P-wave anisotropy tomography. Prominent low-velocity (low-V ) and high-attenuation (low-Q) zones are revealed in the crust and uppermost mantle beneath active arc and back-arc volcanoes and they extend to the deeper portion of the mantle wedge, indicating that the low-V /low-Q zones form the sources of arc magmatism and volcanism, and the arc magmatic system is related to deep processes such as convective circulation in the mantle wedge and dehydration reactions in the subducting slab. Seismic anisotropy seems to exist in all portions of the Northeast Japan subduction zone, including the upper and lower crust, the mantle wedge and the subducting Pacific slab. Multilayer anisotropies with different orientations may have caused the apparently weak shear-wave splitting observed so far, whereas recent results show a greater effect of crustal anisotropy than previously thought. Deep subduction of the Philippine Sea slab and deep dehydration of the Pacific slab are revealed beneath Southwest Japan. Significant structural heterogeneities are imaged in the source areas of large earthquakes in the crust, subducting slab and interplate megathrust zone, which may reflect fluids and/or magma originating from slab dehydration that affected the rupture nucleation of large earthquakes. These results suggest that large earthquakes do not strike anywhere, but in only anomalous areas that may be detected with geophysical methods. The occurrence of deep earthquakes under the Japan Sea and the East Asia margin may be related to a metastable olivine wedge in the subducting Pacific slab. The Pacific slab becomes stagnant in the mantle transition zone under East Asia, and a big mantle wedge (BMW) has formed above the stagnant slab. Convective circulations and fluid and magmatic processes in the BMW may have caused intraplate volcanism (e.g., Changbai and Wudalianchi), reactivation of the North China craton, large earthquakes, and other active tectonics in East Asia. Deep subduction and dehydration of continental plates (such as the Eurasian plate, Indian plate and Burma microplate) are also found, which have caused intraplate magmatism (e.g., Tengchong) and geothermal anomalies above the subducted continental plates. Under Kamchatka, the subducting Pacific slab shortens toward the north and terminates near the Aleutian-Kamchatka junction. The slab loss was induced by friction with the surrounding asthenosphere, as the Pacific plate rotated clockwise 30 Ma ago, and then it was enlarged by the slab-edge pinch-off b...

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“…Although this was a moderate‐size event, its seismic shaking was felt quite widely over a large area of North China, including Beijing, Tianjin and Hebei province. No significant damage was caused by the Wen‐An earthquake, but most people in the region paid much attention to it [ Diao et al , 2006; Lei et al , 2008, 2011]. …”

Section: Introductionmentioning

confidence: 99%

Upper‐mantle tomography and dynamics beneath the North China Craton

Lei

2012

J. Geophys. Res.

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[1] A high-resolution tomographic model of the upper mantle beneath the North China Craton (NCC) is determined using a large number of precisely hand-picked teleseismic P wave arrival times. The results are generally consistent with previous results but high-quality arrivals provide new insights into the dynamics beneath the NCC. Obviously north-south trending low-velocity (low-V) zones are revealed down to $300-400 km depth under the Shanxi rift and Tanlu fault zone, while a north-south trending high-velocity (high-V) zone representing the remainder of detached lithosphere is visible down to $200 km depth under the western portion of eastern NCC. High-V anomalies representing the detached lithosphere are detected at 200-400 km depth under central and eastern NCC. Under the Ordos block high-V anomalies are visible above $400 km depth, indicating intact lithosphere. Broad high-V anomalies representing the stagnant Pacific slab are imaged with a low-V anomaly from Datong volcano to the edge of Bohai Sea in the mantle transition zone beneath eastern and central NCC, suggesting that the Pacific slab has subducted to central NCC but with a gap. A continuously Y-shaped low-V structure is clearly imaged under Datong volcano and Bohai Sea from the lower mantle through this gap in the mantle transition zone to the upper mantle, indicating the existence of a lower mantle plume. These results suggest that in addition to the subduction of the Pacific plate, the plume has also played an important role in lithospheric destruction by thermal erosion of the asthenosphere and detachment of the lithosphere beneath the NCC.

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An attempt to detect temporal variations of crustal structure in the source area of the 2006 Wen-An earthquake in North China

Cited by 10 publications

References 42 publications

Seismic tomographic imaging of the crust and upper mantle under the central and western Tien Shan orogenic belt

Seismic tomographic imaging of the crust and upper mantle under the central and western Tien Shan orogenic belt

Tomography and Dynamics of Western-Pacific Subduction Zones

Upper‐mantle tomography and dynamics beneath the North China Craton

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