The China Earthquake Administration , is mandated by the Law of the People's Republic of China on Protecting Against and Mitigating Earthquake Disasters of PRC to enforce the earthquake administration in the nation under the administration of State Council of the People's Republic of China.Some English text use the name Chinese Seismic Bureau . In older text, it was also referred to by its former name, National Earthquake Bureau or National Seismic Bureau . Wikipedia.
News Article | May 16, 2017
An MS6.4 earthquake occurred in Menyuan County, Haibei Prefecture, Qinghai Province (China) on January 21, 2016, with a moderate strong earthquake following in the area on August 26, 1986. A recent research revealed the seismogenic structure of the 2016 Menyuan earthquake. The study of the relevant thesis entitled "Activity of the Lenglongling fault system and seismotectonics of the 2016 MS 6.4 Menyuan earthquake", published in the recent 2017 SCIENCE CHINA Earth Sciences. The researcher named as Han Zhijun serves as a communications author, who is from Institute of Geology, China Earthquake Administration. The researchers have carried on the analysis of the activity of the Lenglongling fault system and the structural environment of the Menyuan earthquake, and revealed that the Northern Lenglongling fault was a more suitable seismogenic structure for the MS6.4 Menyuan earthquake. The 2016 MS6.4 Menyuan earthquake occurred near the the Lenglongling fault. The earthquake epicenter was distant from the Minle-Damaying and Huangcheng-Shuangta faults, eastern of the Northern Qilian Shan fault zone. A near northwest-striking rupture plane intersects the two faults at a certain angle. The focal mechanism solution shows that this was a thrust-type earthquake, slightly different from the strike-slip movement with a thrust component of the LLLF. Understanding the tectonic environment of the moderate-strong earthquake is of great theoretical and practical significance in evaluating future earthquake risks in the Lenglongling area and determining key areas for future earthquake mitigation. Field geological mapping, tectonic geomorphology analysis, trench excavation and 14C dating reveal that (1) the LLLF has been obviously active since the Holocene, and may behave with characteristic slip behavior and produce MW 7.3-7.5 earthquakes; (2) the LLLF appears as a flower structure in terms of structure style, and dips NNE at a steep angle; and (3) the most recent earthquake event occurred after 1815-1065 a BP. An associated fault, the Northern Lenglongling fault (NLLLF), is located at the northwestern end of the LLLF. Consequently, the NLLLF was continually subject to tectonic pushing effects from the left-lateral shear at the end of the LLLF, and, accordingly, it bent and rotated outward tectonically. Subsequently, the fault deviated from the dominant rupture azimuth and activity weakened. In the late Quaternary, it behaved as a thrust fault with no obvious deformation at the surface. This is indicated by the arc shape, with a micro-protrusion northeastward, and no geologic or geomorphic signs of surface rupturing since the late Quaternary. However, such faults could still rupture at depth, producing moderate-strong earthquakes. The geometric and kinematic properties of the NLLLF are in good agreement with the occurrence and kinematic properties of nodal plane 2, and with the distribution characteristics of the aftershocks and seismic intensity. Therefore, the NLLLF is a more suitable seismogenic structure for the MS 6.4 Menyuan earthquake. In addition, the thrust movement of the NLLLF accommodates subsequent movement of the LLLF. During the historical evolution of the NLLLF, the LLLF and the NLLLF have affected the local topography through tectonic uplift. The result of the research will help to understand the characteristics of the structural environment of the 2016 Menyuan earquake. It is not only significant to understand the activity of the Lenglongling fault, but also to reveal features of the seismogenic structure of the moderate-strong earthquake. This research was funded by the Special Project on Earthquake Research (Grant No. 201408023), and Fundamental Research Funds in Institute of Crustal Dynamics, China Earthquake Administration (Grant No. ZDJ2015-16). See the article: Guo P, Han Z J, An Y F, Jiang W L, Mao Z B, Feng W. 2017. Activity of the Lenglongling fault system and seismotectonics of the 2016 MS6.4 Menyuan earthquake. Science China Earth Sciences, doi: 10.1007/s11430-016-9007-2
News Article | May 4, 2017
North China is one of the areas of strong earthquake activity on the Chinese mainland. In the 1960s~1970s, North China has undergone the 1966 Xingtai Ms7.2, 1969 Bohai Ms7.4, 1975 Haicheng Ms7.3 and 1976 Tangshan Ms7.8 earthquake, causing great losses to people's life and property, where the Tangshan earthquake caused casualties amounted to 240 thousand. In the past 50 years, Chinese seismologists have carried on the large-scale deep geophysical exploration and research, obtained the detailed crustal and upper mantle structure, and revealed the deep tectonic environment of strong earthquake in North China. The related research paper is entitled "Crustal and upper mantle structure and deep tectonic genesis of large earthquakes in North China" published in SCIENCE CHINA Earth Sciences, Vol.60, 2017, wrote by Professor Wang Chunyong at Institute of Geophysics, China Earthquake Administration. The research group reviewed the main achievements of the researches on the crustal and upper mantle structure as well as the seismogenic environment and tectonic patterns in North China since the 1966 Xingtai earthquake. Based on plate tectonics theory, geoscientists have successfully explained the patterns and mechanisms of earthquake activity on the global plate boundaries. However, plate tectonics theory has not explained the occurrence of earthquakes within the continental plate. North China is located within the Asian continent, and the geological structure, seismicity and focal mechanism show that the seismic activity is very different from that in the region of the plate boundary, indicating that the seismotectonics in North China is quite complex. The nucleation, occurence and development of continental earthquakes, and their relationship with the deep-seated structure of the earth are one of the most important subjects in the solid Earth Science. Seismologists have carried out numerous surveys of the crustal and upper mantle structure, and associated studies of seismic tomography in North China, finished 42 deep seismic souding profiles with total length of ~12000 km, and seismic tomography of three-dimensional crustal and upper mantle structure based on the seismic records at ~600 stations. Deep seismic reflection profiling results indicate a complex tectonic setting in the strong earthquake areas of North China, where a listric normal fault and a low-angle detachment in the upper crust coexist with a high-angle deep fault passing through the lower crust to the Moho beneath the hypocenter. Seismic tomography images revealed that the lithospheric structure in North China is highly inhomogeneous, where most of the large earthquakes occurred in the transition between the high- and low-velocity zones, and the Tangshan earthquake area is characterized by a low-velocity anomaly in the middle-lower crust. Comprehensive analysis of geophysical data identified that the deep seismogenic environment in the North China extensional tectonic region is generally characterized by a low-velocity anomalous belt beneath the hypocenter, inconsistency of the deep and shallow structures in the crust, a steep crustalal-scale fault, relative lower velocities in the uppermost mantle, and local Moho uplift. Earthquake prediction is one of the scientific problems in the Earth Science that have not yet been solved. A deep understanding of the deep tectonic environment of strong earthquakes will help to solve the problem of earthquake prediction. Seismologists Deng Qidong (2008) presented that the surface and shallow-deep tectonic features in the large earthquake area have been releaved by the combination of deep seismic reflection profiling and the surface geology and tectonic enviorment, thus we are able to obtain more comprehensive understanding of seismogenic tectonic conditions in the active fold area (the extension zone and the compression zone) of the normal or strike-slip normal fault and the reverse fault. He further pointed out that it is the right direction to combine the surface geological work with the deep structure and the deep material detection, and it is the key to understand the nucleation and occurrence of the large earthquake. The study of deep-seated structure and seismogenic environment in North China is an excellent model of the combination of deep geophysical exploration and surface seismic geologic research. Despite the deep seismic exploration and seismic tomography research has greatly enriched the knowledge of deep-seated structure and seismogenic environment, due to the complexity of continental seismotectonics, we still face some deep-seated problems, which need to further research. Wang C Y, Wu Q J, Duan Y H, Wang Z S, Lou H. 2017. Crustal and upper mantle structure and deep tectonic genesis of large earthquakes in North China. Science China Earth Sciences, 60: 821-857, doi: 10.1007/s11430-016-9009-1
Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 203.66K | Year: 2016
Our overall aim is to build earthquake resilience in China by improving (a) the assessment of seismic hazard and risk from earthquakes and consequent events and (b) the communication and use of probabilistic information in the development of more proportionate and risk-based strategies for disaster risk reduction. We will build on and extend a recently-developed historical catalogue for earthquakes, extend it for the first time to include consequent events (landslides, debris/mud-flows, outburst floods), unify this new database with modern instrumental data, use state-of the art statistical techniques to quantify the associated uncertainties, and incorporate social science-based understanding of risk communication and governance to improve policy development and implementation. The work programme will be carried out in Si-chuan (including the 2008 Wenchuan earthquake) and Yun-nan provinces. While they are both tectonically active, and mountainous, and thus vulnerable not only to earthquakes but also to consequent hazards of earthquake-triggered landslides and flooding, Si-chuan is one of the wealthiest provinces in China, while Yun-nan is one of poorest. These differences in wealth, combined with the recency of the devastating 2008 Wenchuan in Si-chuan compared to the more attenuated memory of the 1996 Lijiang earthquake in Yun-nan, make for a natural experiment in which to test the efficacy of improved probabilistic assessment of risk and associated uncertainty to people and property by earthquakes, and consequent event hazards, in supporting more risk-based approaches to disaster reduction. This project will promote long-term sustainable growth in earthquake prone regions of China by improving both the assessment of earthquake hazard and consequent event risk and the communication, understanding, and use of the resulting probabilistic forecasts for disaster risk reduction by policymakers and local publics. It addresses several specific capacity gaps identified in successive Chinese national disaster risk reduction strategies. As well as engaging with policymakers at both the national and local levels to improve the effectiveness of emergency planning and building code regulation, we will also engage directly with local publics to enhance public understanding of risk and capacity to deal with it. In so doing, the project will also fulfil the UKs Official Development Assistance (ODA) commitment to promoting the economic development and welfare of developing countries by drawing on UKs science base to address a key vulnerability differentially affecting the very poorest in China.
Zhang L.,China Earthquake Administration |
He C.,China Earthquake Administration
Tectonophysics | Year: 2013
We investigated the properties of frictional sliding of natural gouges collected from Longmenshan fault zone which ruptured during the Wenchuan Mw7.9 earthquake. Based on XRD analysis, five gouge samples of different mineralogical assemblies and mineral contents are chosen for frictional sliding experiments with initial confining pressure of 50. MPa and at different temperatures from 25. °C to 150. °C. To obtain the rate dependence of friction, shearing rates are stepped up and down in the range of 0.0488 to 6.1. μm/s. While the friction coefficient of most gouge samples decreases with the clay content following a general trend consistent with previous studies, the organic-matter-bearing sample (PX-3) shows a much lower value than the prediction by the general trend, indicating further strength reduction due to the ~ 9% organic matter included. We also found a significant effect of temperature on the sliding behavior of organic-matter-bearing and carbonate-rich gouges. When temperature increases to 150. °C, the PX-3 sample (with organic matter) exhibits unstable oscillation that indicates velocity-weakening frictional sliding behavior, in contrast to the velocity-strengthening behavior at lower temperatures. The velocity dependence of carbonate-rich samples (PX-1, PX-2) with more than 50. wt.% carbonates is also sensitive to temperature and shearing rates, and both samples have smaller velocity dependence of friction (a-b) at higher temperatures. The (a-. b) value of the PX-2 sample (with ~ 80% carbonates) even decreases to the velocity neutral point at 150. °C and slow shearing rates. Based on the rate and state friction framework, fast slip nucleation is possible for faults associated with the organic-matter-bearing gouge at 150. °C, whereas triggered seismic slips are possible in faults that include the carbonate-rich samples which have a small (a-b) value at 150. °C. The temperature-dependent sliding behavior of carbonate-dominant and organic-matter-bearing gouges probably provides a new clue to the problem of transition from shallow aseismic zone to seismic zone in subduction interfaces of the oceanic plate. © 2013 Elsevier B.V.
Zhang P.-Z.,China Earthquake Administration
Tectonophysics | Year: 2013
One of remarkable geological and geomorphological features in continental China is the presence of a north-south trending tectonic zone which separates the seismically active Tibetan Plateau to the west from the tectonically stable South China and Ordos blocks to the east. The zone also owns a name of "north-south seismic belt" as a large number of great historical earthquakes occur on it. The most recent one, the 2008 Wenchuan earthquake, attests its recent tectonic activity. In this review I take the Western Sichuan region as an example to probe the structural styles and kinematic pattern as well as deep geological process associated with tectonic deformation of the north-south trending zone. Through integrated studies on active faults, GPS crustal deformation, and geophysical structure, we show that deformation in the Western Sichuan is governed by interactions among three crustal blocks (Songpan, Chuandian, and South China) of distinctive rheological properties under the tectonic framework that eastward growth of the "soft" Eastern Tibet is blocked by the "hard" lithosphere of the South China block. The left-lateral Xianshuihe Fault continues to the north-south trending fault system without crustal shortening to form a bounding fault to limit the northern extend of the magnificent clockwise rotation of crustal material around the Eastern Himalaya Syntax. Upper crust of the three blocks is dominated by brittle deformation, whereas the ductile flow of lower crust would drag the brittle upper crustal blocks to move with respect to each other. The relative motions among the brittle upper crustal blocks cause strain accumulations among their bounding faults to generate large earthquakes. Deformation of the Western Sichuan region can thus be described in terms of combined model of rigid block movement and continuous deformation. We suggest this combined model can be applied to entire continental China. © 2012 .
Lei J.,China Earthquake Administration
Journal of Geophysical Research: Solid Earth | Year: 2011
Detailed 3-D tomographic images of P and S wave velocity (Vp, Vs) and Poisson's ratio (σ) 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-σ 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-σ 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-σ 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-σ 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-σ anomalies are revealed in the upper crust, while high-Vp, high-Vs, and low-σ 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- anomalies in the upper and middle crust, while western Tien Shan exhibits low-Vp, low-Vs, and high-σ 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. Copyright 2011 by the American Geophysical Union.
Lei J.,China Earthquake Administration
Journal of Geophysical Research: Solid Earth | Year: 2012
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. © 2012 American Geophysical Union. All Rights Reserved.
Xu C.,China Earthquake Administration
Geoscience Frontiers | Year: 2015
Inventory maps of earthquake-triggered landslides can be constructed using several methods, which are often subject to obvious differences due to lack of commonly accepted criteria or principles. To solve this problem, the author describes the principles for preparing inventory maps of earthquake-triggered landslides, focusing on varied methods and their criteria. The principles include the following key points: all landslides should be mapped as long as they can be recognized from images; both the boundary and source area position of landslides should be mapped; spatial distribution pattern of earthquake-triggered landslides should be continuous; complex landslides should be divided into distinct groups; three types of errors such as precision of the location and boundary of landslides, false positive errors, and false negative errors of earthquake-triggered landslide inventories should be controlled and reduced; and inventories of co-seismic landslides should be constructed by the visual interpretation method rather than automatic extraction of satellite images or/and aerial photographs. In addition, selection of remote sensing images and creation of landslides attribute database are also discussed in this paper. Then the author applies these principles to produce inventory maps of four events: the 12 May 2008 Wenchuan, China Mw 7.9, 14 April 2010 Yushu, China Mw 6.9, 12 January 2010 Haiti Mw 7.0, and 2007 Aysén Fjord, Chile Mw 6.2. The results show obvious differences in comparison with previous studies by other researchers, which again attest to the necessity of establishment of unified principles for preparation of inventory maps of earthquake-triggered landslides. © 2015 China University of Geosciences (Beijing) and Peking University.
Xu C.,China Earthquake Administration
Geomorphology | Year: 2014
Gorum et al. (2013, Geomorphology 184, 127-138) carried out a study on inventory compilation and statistical analyses of landslides triggered by the 2010 Mw 7.0 Haiti earthquake. They revealed that spatial distribution patterns of these landslides were mainly controlled by complex rupture mechanism and topography. They also suggested that blind-rupture earthquakes trigger fewer landslides than surface-rupture earthquakes on thrust reverse faults. Although a few lines of evidence indicate that buried-rupture earthquakes might trigger fewer landslides than surface-rupture earthquakes on reverse faults, more careful comparisons and analyses indicate that it is not always true. Instead, some cases show that a buried-rupture earthquake can trigger a larger quantity of landslides that are distributed in a larger area, whereas surface-rupture earthquakes can trigger larger but a fewer landslides distributed in a smaller area. © 2014 Elsevier B.V.
Du X.B.,China Earthquake Administration
Science China Earth Sciences | Year: 2011
Two types of changes in apparent resistivity (AR) have been linked to earthquake occurrences. This paper studies the changes and their causes, in detail with the ultimate purpose of developing and assessing a method of earthquake (EQ) prediction. The AR changes of the first type (CFT) are considered to be precursors related to earthquakes (EQs); these appear mostly in the medium-term period before EQs and in the short-term period preceding EQs. The changes of the second type (CST) are characterized by a turning anomaly of a long-trend AR variation or the drastically descending/ascending anomaly superimposed on such a variation; these appear synchronously in large areas, such as the Chinese mainland, and northern and northwestern China, ect. Their spatio-temporal clusters correspond well to high seismicities in the areas and distant great EQs around the Chinese mainland. Based on the behaviors of the two types of changes, the AR changes observed prior to the Ms8. 0 Wenchuan EQ of 2008 are studied. The results show that in the medium-term period before the EQ, noticeable anomalies appeared synchronously at four stations around the Songpan-Ganzi active block, but only weak upward changes were observed in the short-term period preceding the EQ, which caused the prediction of the imminent EQ to fail. © 2010 Science China Press and Springer-Verlag Berlin Heidelberg.