The identification of large-giant bedrock landslides triggered by earthquake aims to the landslide prevention and control. Previous studies have described the basic characteristics, distribution, and the formation mec...The identification of large-giant bedrock landslides triggered by earthquake aims to the landslide prevention and control. Previous studies have described the basic characteristics, distribution, and the formation mechanism of seismic landslides （Bijan Khazai et al., 2003; Chong Xu et al., 2013; Lewis a. Owen et al., 2008; Randall W. Jibson et al., 2006）. However, few researches have focused on the early identification indicators of large-giant bedrock landslides triggered by earthquake （David k. Keefer., 1984; Janusz Wasowski et al., 2011; Alexander L.Strom., 2009; Patrick Meunier et al., 2008; Shahriar Vahdani et al., 2002; Bijan Khazai et al., 2003）. This paper presents the identification indicators of large-giant bedrock landslides triggered by earthquake in the Longmenshan tectonic belt on the basic of their characteristics, distribution and the relationship between seismic landslides and the peak ground motion acceleration.展开更多
On Jan.31 of 2010,the Suining earthquake occurred at Suining City whch is located the center of Sichuan Basin.It is unusual for the strong earthquake to occur at the center of Sichuan Basin with a stable geotectonic e...On Jan.31 of 2010,the Suining earthquake occurred at Suining City whch is located the center of Sichuan Basin.It is unusual for the strong earthquake to occur at the center of Sichuan Basin with a stable geotectonic environment and a low-level historical seismicity.The macro-epicenter of the earthquake is located at Moxi town of Suining city,Sichuan province,China.The earthquake intensity of the epicenter area is degree VII,and the long axis of the isoseismal line trends in NE orientation.The Suining earthquake caused the collapse or destruction of 460 family houses.The earthquake focal mechanism solution and records of the near-field seismographic stations showed the earthquake occurred at the reverse fault at a depth 34 km.Based on the waveform and focal mechanism,we consider the Suning earthquake is triggered by the reverse fault and not by the gravitational collapse or man-made explosive sources.Basing on seismic refraction profile and borehole,we consider that the earthquake is triggered by the backthrust fault of Moxi anticline rooted in detachments at a depth 3-4 km.Furthermore,we infer that tectonic mechanism of the Suining(Ms5.0) Earthquake is driven by the horizontal crustal shortening and stress adjustment on a shallow detachment after the Wenchuan(Ms 8.0) earthquake.展开更多
This paper expounds the quantitative tectonic indicators and some qualitative indicators of large earthquakes in the coast areas of Fujian, Guangdong, Taiwan and Hainan. The main quantitative indicators include uplift...This paper expounds the quantitative tectonic indicators and some qualitative indicators of large earthquakes in the coast areas of Fujian, Guangdong, Taiwan and Hainan. The main quantitative indicators include uplift amplitude of the Moho, Quaternary and Late Holocene coasts. The paper also gives a brief account of the research method on quantitative indicators of surface uplifted zones. Taiwan is a famous neotectonic zone and an area of large earthquakes in the world. There is only one large-earthquake area in each of Fujian, Guangdong and Hainan Provinces. Along the coast large earthquake areas there are certainly many remains of crustal activity. Among these remains, coast activity, taking the sea level as the accurate marker horizon, can determine not only the amplitude of coastal elevation and subsidence in a certain period, but also the cycle and rate of positive or negative movements.展开更多
The Bayan Har block is mainly bounded by the east Kunlun fault zone to the north, Garze-Yushu -Xianshuihe fault zone to the south and Longmenshan fault zone to the east （Fig. 1）. In the past 20 years, large earthqua...The Bayan Har block is mainly bounded by the east Kunlun fault zone to the north, Garze-Yushu -Xianshuihe fault zone to the south and Longmenshan fault zone to the east （Fig. 1）. In the past 20 years, large earthquakes have occurred frequently along this block＇s boundaries, which has received much attention among geoscientists. Whether large earthquakes will happen （and where） along this block＇s boundary faults in the future are two key problems that need to be addressed. This study calculates the accumulated tectonic stress and superposition of the coulomb stress caused by fault slip of 16 large earthquakes since 1904, and evaluates the possible locations of future earthquakes that may occur around this block.展开更多
The Sierras de Cordoba are the easternmost uplifted ranges of the Sierras Pampeanas geological province of Argentina. They are composed of a Neoproterozoic-Paleozoic basement arranged in north-south aligned mountain r...The Sierras de Cordoba are the easternmost uplifted ranges of the Sierras Pampeanas geological province of Argentina. They are composed of a Neoproterozoic-Paleozoic basement arranged in north-south aligned mountain ranges, limited by west-vergent reverse faults, reactivated or formed by compressive tectonics during the Andean orogeny. The ranges are also affected by oblique subvertical lineaments,probably related to pan-Gondwanan structures. The recorded seismicity shows anomalously deep earthquakes（up to 80 km depth） concentrated in the northwestern area. We attribute this seismicity to the current tectonic activity of the Ojo de Agua Lineament. This lineament is a N13°-135° strike, 70°-80° NE dip,macrostructure with more than 80 km depth and 160 km length. A sinistral transcompressional kinematics（convergent oblique shear） is deduced by the focal mechanism of a deep earthquake, together with hydrological and geomorphological features strongly modified. The continental lithosphere under the Sierras de Cordoba would be colder and more rigid than in a normal subduction area, due to the retraction of the asthenospheric wedge to the foreland, causing seismicity to depths greater than 40 km, below the Mohorovicic discontinuity. Neogene volcanism would be closely related to this lineament, allowing the rapid ascent of melts from the mantle.展开更多
The regional tectonic background and characteristics of active faults of the Yutian MS7.3earthquake on February 12,2014 are discussed in this paper.After the analysis of the epicenter area of the MS7.3 earthquake in 2...The regional tectonic background and characteristics of active faults of the Yutian MS7.3earthquake on February 12,2014 are discussed in this paper.After the analysis of the epicenter area of the MS7.3 earthquake in 2014 and the focal mechanisms of the former strong earthquakes around it,the authors deduced that the seismogenic fault of the MS7.3earthquake is the east branch of the Ashikule fault.The MS7.3 earthquake in 2014 and the MS7.3 earthquake in 2008 are two strong earthquake events on the different sections of the Altun Tagh fault,where the fault behavior changes from sinistral slip to normal faulting because of the extensional tail effects in the southern end of the Altun Tagh fault.It is concluded that the two MS7.3 earthquakes have the same dynamic source,and the MS7.3earthquake in 2008 promoted the occurrence of the MS7.3 earthquake in 2014.Finally,we calculate the Coulomb stress change to the seismogenic fault of the MS7.3 earthquake in2014 from the MS7.3 earthquake in 2008 using the layered crust model.The result also shows that the MS7.3 earthquake in 2008 accelerated the occurrence of the MS7.3earthquake in 2014.展开更多
Earthquake prediction remains a challenging and difficult task for scientists all over the world.The tidal triggering of earthquakes is being proven by an increasing number of investigations,most of which have shown t...Earthquake prediction remains a challenging and difficult task for scientists all over the world.The tidal triggering of earthquakes is being proven by an increasing number of investigations,most of which have shown that earthquakes are positively correlated with tides,and thus,tides provide a potential tool for earthquake prediction,especially for imminent earthquakes.In this study,publications concerning the tidal triggering of earthquakes were compiled and analyzed with regard to global earthquakes,which were classified into three main types:tectonic,volcanic,and slow earthquakes.The results reveal a high correlation between tectonic earthquakes and tides(mainly for semidiurnal and diurnal tides;14-day tides) before and after the occurrence of significant earthquakes.For volcanic earthquakes,observations of volcanoes on the seafloor and land indicate that volcanic earthquakes in near-shore volcanic areas and mid-ocean ridges have a strong correlation with tidal forces,mostly those with semidiurnal and diurnal periods.For slow earthquakes,the periodicity of the tremor duration is highly correlated with semidiurnal and diurnal tides.In conclusion,the tidal triggering of these three types of earthquakes makes a positive contribution to earthquake preparation and understanding the triggering mechanism,and thus,the prediction of these types of earthquakes should be investigated.However,there are still several inadequacies on this topic that need to be resolved to gain a definitiveanswer regarding the tidal triggering of all earthquakes.The main inadequacies are discussed in this paper from our point of view.展开更多
The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by...The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area. We relocated those earthquakes with the double-difference method. Based on the assumption that clustered small earthquakes often occur in the vicinity of fault plane of large earthquake, and referring to the morphology of the long axis of the isoseismal line obtained by the predecessors, we selected a strip-shaped zone from the relocated earthquake catalog in the period from 1980 to 2009 to invert fault plane parameters of this earthquake. The inversion results are as follows： the strike is 38.23°, the dip angle is 82.54°, the slip angle is -156.08°, the fault length is about 80 km, the lower-boundary depth is about 23 km and the buried depth of upper boundary is about 3 kin. This shows that the seismogenic fault is a NNE-trending normal dip-slip fault, southeast wall downward and northwest wall uplift, with the right-lateral strike-slip component. Moreover, the surface rupture zone, intensity distribution of the earth-quake and seismic-wave velocity profile in the focal area all verified our study result.展开更多
In this study, we analyzed the gravity and, magnetic characteristics, and the occurrence of a fault zone and discussed the relationships between the two locations. The results reveal that the subsurface structures str...In this study, we analyzed the gravity and, magnetic characteristics, and the occurrence of a fault zone and discussed the relationships between the two locations. The results reveal that the subsurface structures strikes are different compared with those in the research region. In other words, the geophysical advantageous directions from the gravity and magnetic anomalies are not the same as those caused by the surface structures. The local horizontal gradient results from the gravity and magnetic anomalies show that the majority of earthquakes occur along an intense fault zone, which is a zone of abrupt gravity and negative magnetic change, where the shapes match very well. From the distribution of earthquakes in this area, we find that it has experienced more than 11 earthquake events with magnitude larger than Ms7.0. In addition, water development sites such as Jinshajiang, Lancangjiang, and the Red River and Pearl River watersheds have been hit ten times by earthquakes of this magnitude. It is observed that strong earthquakes occur frequently in the Holocene active fault zone.展开更多
The relationship between gravity variation and the Akto Ms6.7 earthquake on November 11, 2016, was studied by use of mobile gravity observation data from the China continental structural environmental monitoring netwo...The relationship between gravity variation and the Akto Ms6.7 earthquake on November 11, 2016, was studied by use of mobile gravity observation data from the China continental structural environmental monitoring network. The result revealed that before the Akto earthquake, a high positive gravity variation was observed in the Pamir tectonic knots region （within a maximum magnitude of approximately ＋80 microgal）, which was consistent with the existing knowledge of gravity abnormality and the locations of strong earthquakes. In view of the recent strong seismic activities in the Pamir tectonic knots region, as well as the strong upward crust movement and compressive strain, it is believed that gravity change in the Pamir tectonic knots region reflects the recent strong seismic activities and crust movement.展开更多
Seismic records produced by different seismic sources vary.In this study,we compared the waveform records and time-frequency characteristics of tectonic earthquakes,artificial explosions,and mine collapses in China’s...Seismic records produced by different seismic sources vary.In this study,we compared the waveform records and time-frequency characteristics of tectonic earthquakes,artificial explosions,and mine collapses in China’s Capital Region.The results show that tectonic earthquakes are characterized by stronger S-wave energy than P-wave energy,obvious high-frequency components,and wide frequency bands of P and S waves.Artificial explosions are characterized by greater P-wave amplitude than S-wave amplitude and near-station surface wave development.Mine collapses are characterized by lower overall frequency,more obvious surface waves,and longer duration.We extracted quantitative discriminants based on the analysis of different event records,with 31 feature values in 7 categories(P/S maximum amplitude ratio,high/low frequency energy ratio,P/S spectral ratio,corner frequency,duration,the second-order moment of spectrum,and energy strongest point).A comparison of the ability of these feature values to recognize distinct events showed that the 6-17 Hz P/S spectral ratio was able to completely distinguish artificial explosions from the other two types of events.The S-wave corner frequency performed relatively well in identifying all three types of events,with an accuracy of over 90%.Additionally,a support vector machine was used to comprehensively distinguish multiple features,with an accuracy for all three types of events reaching up to 100%.展开更多
The MS6.4 Menyuan earthquake occurred on the northern side of the Lenglongling fault(LLLF) in the mid-western of the Qilian-Haiyuan fault zone on January 21, 2016. The earthquake epicenter was distant from the Minle-D...The MS6.4 Menyuan earthquake occurred on the northern side of the Lenglongling fault(LLLF) in the mid-western of the Qilian-Haiyuan fault zone on January 21, 2016. 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. Field geological mapping, tectonic geomorphology analysis, trench excavation and 14 C dating reveal that(1) the LLLF has been obviously active since the Holocene, and may behave with characteristic slip behavior and produce M_W7.3–7.5 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.展开更多
Merapi volcano located in central Java, Indonesia,is one of the most active stratovolcanoes in the world. Many Earth scientists have conducted studies on this volcano using various methods. The geological features aro...Merapi volcano located in central Java, Indonesia,is one of the most active stratovolcanoes in the world. Many Earth scientists have conducted studies on this volcano using various methods. The geological features around Merapi are very attractive to be investigated because they have been formed by a complex tectonic process and volcanic activities since tens of millions of years ago. The southern mountain range, Kendeng basin and Opak active fault located around the study area resulted from these processes. DOMERAPI project was conducted to understand deep magma sources of the Merapi volcano comprehensively. The DOMERAPI network was running from October 2013 to mid-April 2015 by deploying 46 broad-band seismometers around the volcano. Several steps, i.e., earthquake event identification,arrival time picking of P and S waves, hypocenter determination and hypocenter relocation, were carried out in this study. We used Geiger＇s method（Geiger 1912） for hypocenter determination and double-difference method for hypocenter relocation. The relocation result will be used to carry out seismic tomographic imaging of structures beneath the Merapi volcano and its surroundings. For the hypocenter determination, the DOMERAPI data were processed simultaneously with those from the Agency for Meteorology, Climatology and Geophysics（BMKG） seismic network in order to minimize the azimuthal gap. We found that the majority of earthquakes occurred outside the DOMERAPI network. There are 464 and 399 earthquakes obtained before and after hypocenter relocation, respectively. The hypocenter relocation result successfully detects some tectonic features, such as a nearly vertical cluster of events indicating a subduction-related backthrust to the south of central Java and a cluster of events to the east of Opak fault suggesting that the fault has an eastward dip.展开更多
Earthquake early warning(EEW)is one of the important tools to reduce the hazard of earthquakes.In contemporary seismology,EEW is typically transformed into a fast classification of earthquake magnitude,i.e.,large magn...Earthquake early warning(EEW)is one of the important tools to reduce the hazard of earthquakes.In contemporary seismology,EEW is typically transformed into a fast classification of earthquake magnitude,i.e.,large magnitude earthquakes that require warning are in the positive category and vice versa in the negative category.However,the current standard information signal processing routines for magnitude fast classification are time-consuming and vulnerable to data imbalance.Therefore,in this study,Deep Learning(DL)algorithms are introduced to assist with EEW.For the three-component seismic waveform record of 7 s obtained from the China Earthquake Network Center(CENC),this paper proposes a DL model(EEWMagNet),which accomplishes the extraction of spatial and temporal features through DenseBlock with Bottleneck and Multi-Head Attention.Extensive experiments on Chinese field data demonstrate that the proposed model performs well in the fast classification of magnitude.Moreover,the comparison experiments demonstrate that the epicenter distance information is indispensable,and the normalization has a negative effect on the model to capture accurate amplitude information.展开更多
The purpose of this research is to demonstrate the use of Adaptive Neuro-Fuzzy Inference System(ANFIS)for discrimination between quarry blasts and microearthquakes in the Tehran region using data from the Broadband Ir...The purpose of this research is to demonstrate the use of Adaptive Neuro-Fuzzy Inference System(ANFIS)for discrimination between quarry blasts and microearthquakes in the Tehran region using data from the Broadband Iranian National Network Center(BIN).In the south and southeast of Tehran,a large number of quarry blasts“contaminate”the earthquake catalog.In order to identify the real seismicity(tectonic earthquakes)in the region,we need to discriminate quarry blasts from natural earthquakes in the catalog.展开更多
基金financially supported by the Geological Survey Project of China Geological Survey (grant no.1212011014032,1212011220134)
文摘The identification of large-giant bedrock landslides triggered by earthquake aims to the landslide prevention and control. Previous studies have described the basic characteristics, distribution, and the formation mechanism of seismic landslides （Bijan Khazai et al., 2003; Chong Xu et al., 2013; Lewis a. Owen et al., 2008; Randall W. Jibson et al., 2006）. However, few researches have focused on the early identification indicators of large-giant bedrock landslides triggered by earthquake （David k. Keefer., 1984; Janusz Wasowski et al., 2011; Alexander L.Strom., 2009; Patrick Meunier et al., 2008; Shahriar Vahdani et al., 2002; Bijan Khazai et al., 2003）. This paper presents the identification indicators of large-giant bedrock landslides triggered by earthquake in the Longmenshan tectonic belt on the basic of their characteristics, distribution and the relationship between seismic landslides and the peak ground motion acceleration.
基金the National Natural Science Foundation of China (Grant No. 40841010,40972083,41172162)the National Science and Technology Support Program (Grant nNo. 2006BAC13B02-107,2006BAC13B01-604) for the funding
文摘On Jan.31 of 2010,the Suining earthquake occurred at Suining City whch is located the center of Sichuan Basin.It is unusual for the strong earthquake to occur at the center of Sichuan Basin with a stable geotectonic environment and a low-level historical seismicity.The macro-epicenter of the earthquake is located at Moxi town of Suining city,Sichuan province,China.The earthquake intensity of the epicenter area is degree VII,and the long axis of the isoseismal line trends in NE orientation.The Suining earthquake caused the collapse or destruction of 460 family houses.The earthquake focal mechanism solution and records of the near-field seismographic stations showed the earthquake occurred at the reverse fault at a depth 34 km.Based on the waveform and focal mechanism,we consider the Suning earthquake is triggered by the reverse fault and not by the gravitational collapse or man-made explosive sources.Basing on seismic refraction profile and borehole,we consider that the earthquake is triggered by the backthrust fault of Moxi anticline rooted in detachments at a depth 3-4 km.Furthermore,we infer that tectonic mechanism of the Suining(Ms5.0) Earthquake is driven by the horizontal crustal shortening and stress adjustment on a shallow detachment after the Wenchuan(Ms 8.0) earthquake.
基金This project was sponsored by the Joint Seismological Science Foundation Grant 2296203
文摘This paper expounds the quantitative tectonic indicators and some qualitative indicators of large earthquakes in the coast areas of Fujian, Guangdong, Taiwan and Hainan. The main quantitative indicators include uplift amplitude of the Moho, Quaternary and Late Holocene coasts. The paper also gives a brief account of the research method on quantitative indicators of surface uplifted zones. Taiwan is a famous neotectonic zone and an area of large earthquakes in the world. There is only one large-earthquake area in each of Fujian, Guangdong and Hainan Provinces. Along the coast large earthquake areas there are certainly many remains of crustal activity. Among these remains, coast activity, taking the sea level as the accurate marker horizon, can determine not only the amplitude of coastal elevation and subsidence in a certain period, but also the cycle and rate of positive or negative movements.
基金supported by Geological Survey programs from Geological Survey of China(No.1212011120163 and 12120114002101)Basic Science Research Fund of the Institute of Geomechanics,CAGS (No.DZLXJK201212)National Natural Science Foundation of China (No.41171009)
文摘The Bayan Har block is mainly bounded by the east Kunlun fault zone to the north, Garze-Yushu -Xianshuihe fault zone to the south and Longmenshan fault zone to the east （Fig. 1）. In the past 20 years, large earthquakes have occurred frequently along this block＇s boundaries, which has received much attention among geoscientists. Whether large earthquakes will happen （and where） along this block＇s boundary faults in the future are two key problems that need to be addressed. This study calculates the accumulated tectonic stress and superposition of the coulomb stress caused by fault slip of 16 large earthquakes since 1904, and evaluates the possible locations of future earthquakes that may occur around this block.
基金The CONICET(PIP 00628,PUE 2016-CICTERRA)FONCyT(PID-00013)+1 种基金SECyT-UNC(05/1641)Institute of Aging are thanked for supporting our research
文摘The Sierras de Cordoba are the easternmost uplifted ranges of the Sierras Pampeanas geological province of Argentina. They are composed of a Neoproterozoic-Paleozoic basement arranged in north-south aligned mountain ranges, limited by west-vergent reverse faults, reactivated or formed by compressive tectonics during the Andean orogeny. The ranges are also affected by oblique subvertical lineaments,probably related to pan-Gondwanan structures. The recorded seismicity shows anomalously deep earthquakes（up to 80 km depth） concentrated in the northwestern area. We attribute this seismicity to the current tectonic activity of the Ojo de Agua Lineament. This lineament is a N13°-135° strike, 70°-80° NE dip,macrostructure with more than 80 km depth and 160 km length. A sinistral transcompressional kinematics（convergent oblique shear） is deduced by the focal mechanism of a deep earthquake, together with hydrological and geomorphological features strongly modified. The continental lithosphere under the Sierras de Cordoba would be colder and more rigid than in a normal subduction area, due to the retraction of the asthenospheric wedge to the foreland, causing seismicity to depths greater than 40 km, below the Mohorovicic discontinuity. Neogene volcanism would be closely related to this lineament, allowing the rapid ascent of melts from the mantle.
基金funded by the Spark Program of Earthquake Science of China(XH15047Y)the National Science Foundation of China(41404043)
文摘The regional tectonic background and characteristics of active faults of the Yutian MS7.3earthquake on February 12,2014 are discussed in this paper.After the analysis of the epicenter area of the MS7.3 earthquake in 2014 and the focal mechanisms of the former strong earthquakes around it,the authors deduced that the seismogenic fault of the MS7.3earthquake is the east branch of the Ashikule fault.The MS7.3 earthquake in 2014 and the MS7.3 earthquake in 2008 are two strong earthquake events on the different sections of the Altun Tagh fault,where the fault behavior changes from sinistral slip to normal faulting because of the extensional tail effects in the southern end of the Altun Tagh fault.It is concluded that the two MS7.3 earthquakes have the same dynamic source,and the MS7.3earthquake in 2008 promoted the occurrence of the MS7.3 earthquake in 2014.Finally,we calculate the Coulomb stress change to the seismogenic fault of the MS7.3 earthquake in2014 from the MS7.3 earthquake in 2008 using the layered crust model.The result also shows that the MS7.3 earthquake in 2008 accelerated the occurrence of the MS7.3earthquake in 2014.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB41 000000)the National Natural Science Foundation of China (Grant No. 42174101, 41974023, 41874094, 41874026)。
文摘Earthquake prediction remains a challenging and difficult task for scientists all over the world.The tidal triggering of earthquakes is being proven by an increasing number of investigations,most of which have shown that earthquakes are positively correlated with tides,and thus,tides provide a potential tool for earthquake prediction,especially for imminent earthquakes.In this study,publications concerning the tidal triggering of earthquakes were compiled and analyzed with regard to global earthquakes,which were classified into three main types:tectonic,volcanic,and slow earthquakes.The results reveal a high correlation between tectonic earthquakes and tides(mainly for semidiurnal and diurnal tides;14-day tides) before and after the occurrence of significant earthquakes.For volcanic earthquakes,observations of volcanoes on the seafloor and land indicate that volcanic earthquakes in near-shore volcanic areas and mid-ocean ridges have a strong correlation with tidal forces,mostly those with semidiurnal and diurnal periods.For slow earthquakes,the periodicity of the tremor duration is highly correlated with semidiurnal and diurnal tides.In conclusion,the tidal triggering of these three types of earthquakes makes a positive contribution to earthquake preparation and understanding the triggering mechanism,and thus,the prediction of these types of earthquakes should be investigated.However,there are still several inadequacies on this topic that need to be resolved to gain a definitiveanswer regarding the tidal triggering of all earthquakes.The main inadequacies are discussed in this paper from our point of view.
基金jointly supported by the National Natural Science Foundation of China(Nos.91214201 and 41074072)Research Foundation of Science and Technology Plan Project in Hebei Province(12276903D)
文摘The great Sanhe-Pinggu M8 earthquake occurred in 1679 was the largest surface rupture event recorded in history in the northern part of North China plain. This study determines the fault geometry of this earthquake by inverting seismological data of present-day moderate-small earthquakes in the focal area. We relocated those earthquakes with the double-difference method. Based on the assumption that clustered small earthquakes often occur in the vicinity of fault plane of large earthquake, and referring to the morphology of the long axis of the isoseismal line obtained by the predecessors, we selected a strip-shaped zone from the relocated earthquake catalog in the period from 1980 to 2009 to invert fault plane parameters of this earthquake. The inversion results are as follows： the strike is 38.23°, the dip angle is 82.54°, the slip angle is -156.08°, the fault length is about 80 km, the lower-boundary depth is about 23 km and the buried depth of upper boundary is about 3 kin. This shows that the seismogenic fault is a NNE-trending normal dip-slip fault, southeast wall downward and northwest wall uplift, with the right-lateral strike-slip component. Moreover, the surface rupture zone, intensity distribution of the earth-quake and seismic-wave velocity profile in the focal area all verified our study result.
基金supported by the Chinese Earthquake Administration,Institute of Seismology Foundation(IS201326126)Chinese earthquake scientific array exploration northern section of North South Seismic Belt gravity profile Foundation(201308011)
文摘In this study, we analyzed the gravity and, magnetic characteristics, and the occurrence of a fault zone and discussed the relationships between the two locations. The results reveal that the subsurface structures strikes are different compared with those in the research region. In other words, the geophysical advantageous directions from the gravity and magnetic anomalies are not the same as those caused by the surface structures. The local horizontal gradient results from the gravity and magnetic anomalies show that the majority of earthquakes occur along an intense fault zone, which is a zone of abrupt gravity and negative magnetic change, where the shapes match very well. From the distribution of earthquakes in this area, we find that it has experienced more than 11 earthquake events with magnitude larger than Ms7.0. In addition, water development sites such as Jinshajiang, Lancangjiang, and the Red River and Pearl River watersheds have been hit ten times by earthquakes of this magnitude. It is observed that strong earthquakes occur frequently in the Holocene active fault zone.
基金jointly supported by the the special earthquake research grant offered by the China Earthquake Administration(201508009,201308009)the Director Foundation of Institute of Seismology,China Earthquake Administration(IS201326121)
文摘The relationship between gravity variation and the Akto Ms6.7 earthquake on November 11, 2016, was studied by use of mobile gravity observation data from the China continental structural environmental monitoring network. The result revealed that before the Akto earthquake, a high positive gravity variation was observed in the Pamir tectonic knots region （within a maximum magnitude of approximately ＋80 microgal）, which was consistent with the existing knowledge of gravity abnormality and the locations of strong earthquakes. In view of the recent strong seismic activities in the Pamir tectonic knots region, as well as the strong upward crust movement and compressive strain, it is believed that gravity change in the Pamir tectonic knots region reflects the recent strong seismic activities and crust movement.
文摘Seismic records produced by different seismic sources vary.In this study,we compared the waveform records and time-frequency characteristics of tectonic earthquakes,artificial explosions,and mine collapses in China’s Capital Region.The results show that tectonic earthquakes are characterized by stronger S-wave energy than P-wave energy,obvious high-frequency components,and wide frequency bands of P and S waves.Artificial explosions are characterized by greater P-wave amplitude than S-wave amplitude and near-station surface wave development.Mine collapses are characterized by lower overall frequency,more obvious surface waves,and longer duration.We extracted quantitative discriminants based on the analysis of different event records,with 31 feature values in 7 categories(P/S maximum amplitude ratio,high/low frequency energy ratio,P/S spectral ratio,corner frequency,duration,the second-order moment of spectrum,and energy strongest point).A comparison of the ability of these feature values to recognize distinct events showed that the 6-17 Hz P/S spectral ratio was able to completely distinguish artificial explosions from the other two types of events.The S-wave corner frequency performed relatively well in identifying all three types of events,with an accuracy of over 90%.Additionally,a support vector machine was used to comprehensively distinguish multiple features,with an accuracy for all three types of events reaching up to 100%.
基金supported by a Special Project on Earthquake Research, the China Active Fault Survey Project-The South-North Seismic Zone Northern Segment (Grant No. 201408023)Fundamental Research Funds in Institute of Crustal Dynamics, China Earthquake Administration (Grant No. ZDJ2015-16)
文摘The MS6.4 Menyuan earthquake occurred on the northern side of the Lenglongling fault(LLLF) in the mid-western of the Qilian-Haiyuan fault zone on January 21, 2016. 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. Field geological mapping, tectonic geomorphology analysis, trench excavation and 14 C dating reveal that(1) the LLLF has been obviously active since the Holocene, and may behave with characteristic slip behavior and produce M_W7.3–7.5 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.
基金Institut de Recherche pour le Développement (IRD), France, for funding the DOMERAPI projectCenter for Volcanology and Geohazard Mitigation as the main counterpart of the DOMERAPI project in Indonesia+1 种基金supported in part by the Indonesian Directorate General of Higher Education (DIKTI) research funding 2015–2016the Institut Teknologi Bandung (ITB) through a WCU research Grant 2016 awarded to SW
文摘Merapi volcano located in central Java, Indonesia,is one of the most active stratovolcanoes in the world. Many Earth scientists have conducted studies on this volcano using various methods. The geological features around Merapi are very attractive to be investigated because they have been formed by a complex tectonic process and volcanic activities since tens of millions of years ago. The southern mountain range, Kendeng basin and Opak active fault located around the study area resulted from these processes. DOMERAPI project was conducted to understand deep magma sources of the Merapi volcano comprehensively. The DOMERAPI network was running from October 2013 to mid-April 2015 by deploying 46 broad-band seismometers around the volcano. Several steps, i.e., earthquake event identification,arrival time picking of P and S waves, hypocenter determination and hypocenter relocation, were carried out in this study. We used Geiger＇s method（Geiger 1912） for hypocenter determination and double-difference method for hypocenter relocation. The relocation result will be used to carry out seismic tomographic imaging of structures beneath the Merapi volcano and its surroundings. For the hypocenter determination, the DOMERAPI data were processed simultaneously with those from the Agency for Meteorology, Climatology and Geophysics（BMKG） seismic network in order to minimize the azimuthal gap. We found that the majority of earthquakes occurred outside the DOMERAPI network. There are 464 and 399 earthquakes obtained before and after hypocenter relocation, respectively. The hypocenter relocation result successfully detects some tectonic features, such as a nearly vertical cluster of events indicating a subduction-related backthrust to the south of central Java and a cluster of events to the east of Opak fault suggesting that the fault has an eastward dip.
基金supported by Fundamental Research Funds for the Central Universities(N2217003)Joint Fund of Science&Technology Department of Liaoning Province,and State Key Laboratory of Robotics,China(2020-KF-12-11)+1 种基金National Natural Science Foundation of China(61902057,41774063)Science for Earthquake Resilience(XH21042).
文摘Earthquake early warning(EEW)is one of the important tools to reduce the hazard of earthquakes.In contemporary seismology,EEW is typically transformed into a fast classification of earthquake magnitude,i.e.,large magnitude earthquakes that require warning are in the positive category and vice versa in the negative category.However,the current standard information signal processing routines for magnitude fast classification are time-consuming and vulnerable to data imbalance.Therefore,in this study,Deep Learning(DL)algorithms are introduced to assist with EEW.For the three-component seismic waveform record of 7 s obtained from the China Earthquake Network Center(CENC),this paper proposes a DL model(EEWMagNet),which accomplishes the extraction of spatial and temporal features through DenseBlock with Bottleneck and Multi-Head Attention.Extensive experiments on Chinese field data demonstrate that the proposed model performs well in the fast classification of magnitude.Moreover,the comparison experiments demonstrate that the epicenter distance information is indispensable,and the normalization has a negative effect on the model to capture accurate amplitude information.
文摘The purpose of this research is to demonstrate the use of Adaptive Neuro-Fuzzy Inference System(ANFIS)for discrimination between quarry blasts and microearthquakes in the Tehran region using data from the Broadband Iranian National Network Center(BIN).In the south and southeast of Tehran,a large number of quarry blasts“contaminate”the earthquake catalog.In order to identify the real seismicity(tectonic earthquakes)in the region,we need to discriminate quarry blasts from natural earthquakes in the catalog.
