Based on the data of the repeated gravity observation network in Chinese mainland since 1998, we analyzed the temporal changes of regional gravity field before the 2008 Yutian Ms7.3 earthquake. The result shows some m...Based on the data of the repeated gravity observation network in Chinese mainland since 1998, we analyzed the temporal changes of regional gravity field before the 2008 Yutian Ms7.3 earthquake. The result shows some mid-to-long term (two to ten years) changes during the earthquake' s preparation. Notable fea- tures are a gravity increase lasting several years and a relatively large-scaled gradient zone of gravity change, the former indicating a continuous energy accumulation and the latter a possible location of seismic rupture. These gravity changes showed a trend of increase-accelerated increase-decelerated increase, similar to that of the Tangshan Ms7.8 earthquake in 1976. The maximum accumulated gravity change related to the earthquake reached 200 × 10 -8 ms -2.展开更多
Based on analysis of the GPS data during 1999-2007,2009-2011,and 2011-2013 mainly from the Crustal Motion Observation Network of China,we obtained the GPS horizontal velocity field,the GPS strain rate field,and the pr...Based on analysis of the GPS data during 1999-2007,2009-2011,and 2011-2013 mainly from the Crustal Motion Observation Network of China,we obtained the GPS horizontal velocity field,the GPS strain rate field,and the profiles across the southwestern segment of the Altyn Tagh Fault zone and its adjacent regions and identified the different characteristics of horizontal crustal deformation fields and profiles during different periods. The results show that,before the February 12,2014,Ms7. 3 Yutian earthquake,the laevorotation deformation along the southwestern segment of the Altyn Tagh Fault zone increased about 3. 3 mm /a during 2011-2013,relative to that in 2009-2011,and the GPS strain rate field distributed in the southeastern segment of the Altyn Tagh Fault during 2011-2013 increased obviously. These abnormal changes may be regarded as precursors to the Ms7. 3 Yutian earthquake.展开更多
The paper inverts the focal mechanism solutions of the Yutian M_S7. 3 main shock,foreshocks and M_S≥3. 5 aftershocks by using the CAP method,based on the broadband waveforms recorded by the Xinjiang and Tibet Digital...The paper inverts the focal mechanism solutions of the Yutian M_S7. 3 main shock,foreshocks and M_S≥3. 5 aftershocks by using the CAP method,based on the broadband waveforms recorded by the Xinjiang and Tibet Digital Seismic Networks. The results show that the M_S7. 3 strong earthquake is of strike-slip type with a normal faulting component,and combined with the analysis of focal structure and the aftershock distribution,the nodal plane I with strike 241°,dip 90° and rake- 22° is considered to be the seismogenic fault plane of the main shock. The direction of P-axis for the main shock is 194°,close to the near NS direction of the principal stress P-axis of historical strong earthquakes in this region. The focal mechanism solution of the M_S5. 4 foreshock has a good consistency with that of the main shock. Among the 18 aftershocks,10 are of strike-slip type,6 are of normal faulting type and 2 are of thrust type. 70% of the aftershocks in the sequence have a focal mechanism with P-axis in the near-NS direction. The focal depths of this M_S7. 3 earthquake sequences are distributed in the range of 5km- 28 km,with the majority in the depth range of 15km- 20 km,slightly deeper than the depth of 10 km of the main shock as calculated.展开更多
The M_S7. 3 earthquake occurred in Yutian,Xinjiang on February 12,2014. Based on seismic waveform data before the earthquake and aftershocks of the earthquake sequence,which were recorded by the Xinjiang Regional Digi...The M_S7. 3 earthquake occurred in Yutian,Xinjiang on February 12,2014. Based on seismic waveform data before the earthquake and aftershocks of the earthquake sequence,which were recorded by the Xinjiang Regional Digital Seismic Network, this paper corrected instrument response,propagation path and site response of the S-wave recording spectra. We then calculated with genetic algorithms,on the basis of the Brune model,the source parameters of the 102 M_L≥3. 0 Yutian earthquake sequence,seismic moment,apparent stress and corner frequency. The results show that,seismic moment of the earthquake sequence is between 3. 46 × 10~11- 2. 08 × 10~15N·m,apparent stress is between1. 48 × 10~5- 1. 16 × 10~6 Pa,mean stress level is 0. 31 MPa,and corner frequency is between1. 4- 7. 1Hz in the range of 3. 0- 5. 0. By analyzing the apparent stress and corner frequency variation with time,we obtain that apparent stress of earthquakes before the Yutian M_S7. 3 earthquake was significantly higher than the aftershock sequence,but the corner frequency was significantly lower than the aftershock sequence. Apparent stress was at a high level before the main shock, which shows that the main shock zone accumulated higher stress,and then the apparent stress was reduced. The main shock occurred in the process of slow increase. Because of the release of a large amount of stress,after the M_S7. 3 earthquake,the apparent stress was gradually reduced. That was the performance of low stress fracture of aftershocks.展开更多
After the Yutian M_S7.3 earthquake,the authors instantly collected 1Hz high frequency data of the 4 reference stations within 350 km around the epicenter,and calculated the GNSS data with the TRACK module. The results...After the Yutian M_S7.3 earthquake,the authors instantly collected 1Hz high frequency data of the 4 reference stations within 350 km around the epicenter,and calculated the GNSS data with the TRACK module. The results showed that:( 1) The co-seismic displacement of Yutian station,about 54 km from the epicenter,is the most obvious,particularly in the EW component,with a change of about 52.5 ± 11mm,which is more than three times the mean-square error of calculating precision.( 2) In the Yutian reference station,the biggest variation in the EW component appeared within 1 minute after the earthquake.( 3) The change in the NS component is not great.展开更多
On February 12,2014,a large Mw7. 3 earthquake occurred in Yutian of Xijiang Province,China.We processed the global ionosphere maps provided by CODE( the Center for Orbit Determination in Europe)and the foF2( the cr...On February 12,2014,a large Mw7. 3 earthquake occurred in Yutian of Xijiang Province,China.We processed the global ionosphere maps provided by CODE( the Center for Orbit Determination in Europe)and the foF2( the critical frequency of F2-layer) data of Chongqing ionosonde station to analyze the preearthquake ionospheric anomalies. Solar activities and magnetic storm were checked by the sliding inter quartile range method to remove their effects on the ionosphere. A positive ionospheric anomaly with the large amplitude of 20 TECU was observed near the epicenter on February 3( 10th day before the earthquake). In addition,the foF2 at Chongqing station had an unusual increase of more than 40% on the day,which was consistent with the TEC( Total Electron Content) anomaly. The global disturbance represents that the peak of TEC anomaly didn’t coincide with the vertical projection of epicenter. The TEC anomalous area was closer to the equator,and it mainly occurred from local time 16 ∶ 00 to 20 ∶ 00. An enhancement of TEC with the small amplitude also appeared in the magnetically conjugated region.展开更多
Earthquake-triggered liquefaction deformation could lead to severe infrastructure damage and associated casualties and property damage.At present,there are few studies on the rapid extraction of liquefaction pits base...Earthquake-triggered liquefaction deformation could lead to severe infrastructure damage and associated casualties and property damage.At present,there are few studies on the rapid extraction of liquefaction pits based on high-resolution satellite images.Therefore,we provide a framework for extracting liquefaction pits based on a case-based reasoning method.Furthermore,five covariates selection methods were used to filter the 11 covariates that were generated from high-resolution satellite images and digital elevation models(DEM).The proposed method was trained with 450 typical samples which were collected based on visual interpretation,then used the trained case-based reasoning method to identify the liquefaction pits in the whole study area.The performance of the proposed methods was evaluated from three aspects,the prediction accuracies of liquefaction pits based on the validation samples by kappa index,the comparison between the pre-and post-earthquake images,the rationality of spatial distribution of liquefaction pits.The final result shows the importance of covariates ranked by different methods could be different.However,the most important of covariates is consistent.When selecting five most important covariates,the value of kappa index could be about 96%.There also exist clear differences between the pre-and post-earthquake areas that were identified as liquefaction pits.The predicted spatial distribution of liquefaction is also consistent with the formation principle of liquefaction.展开更多
The February 12,2014,MS7.3,earthquake in Yutian,Xinjiang,China,occurred as a result of shallow strike-slip faulting in the tectonically complex region of the northern Tibetan Plateau,with a depth of 17 km.This earthqu...The February 12,2014,MS7.3,earthquake in Yutian,Xinjiang,China,occurred as a result of shallow strike-slip faulting in the tectonically complex region of the northern Tibetan Plateau,with a depth of 17 km.This earthquake occurred several hundred kilometers north of the convergent India-Eurasia plate boundary.The epicenter location of the Yutian earthquake,36.1° N,82.5° E,is 110 km north of Yutian County,Hotan Prefecture.A large number of aftershocks from ML2.0 to ML3.0 occurred until 12:00oclock,February 23,2014 and the largest aftershock,MS5.7,occurred at 17:24 p.m.,February 12,2014.The b and h value of Yutian sequence are 0.70 and 1.29,respectively.The waiting time method reveals that the strong aftershocks above ML4.5comply with a linear relationship,which is consistent with the characteristics of a mainshock-aftershock sequence.Furthermore,we calculate the source parameters and analyze the rupture process based on the empirical relationships for the Yutian earthquake,and the results indicate a frictional undershoot behavior in the dynamic source process of the Yutian earthquake,which is also in agreement with the lower and similar b values compared with the 2008 MS7.3 Yutian earthquake and the 2012 MS6.2 Yutian earthquake.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
The basic parameters,seismogenic structure and seismic sequences characteristics of the Yutian MS7. 3 earthquake on February 12,2014 are introduced and compared to the Yutian MS7. 3 earthquake in 2008. The results sho...The basic parameters,seismogenic structure and seismic sequences characteristics of the Yutian MS7. 3 earthquake on February 12,2014 are introduced and compared to the Yutian MS7. 3 earthquake in 2008. The results show that the MS5. 4 earthquake is regarded as an immediate foreshock of the Yutian MS7. 3 main shock. The frequency of strong aftershock sequences was low and their number declined quickly,and the maximum aftershock was a MS5. 7 earthquake. According to analysis of the historical earthquake sequence type,and parameter of h-value,b-value and energy release ratio between main shock and sequence etc.,we found the preliminary conclusion that the Yutian MS7. 3 earthquake sequence in 2014 was a foreshock-main shock-aftershock type.展开更多
On the basis of the previous studies of the layered crustal model in the Yutian area,combined with the field GPS continuous observation data,we roughly estimate the viscous coefficient of each layer. With the viscoela...On the basis of the previous studies of the layered crustal model in the Yutian area,combined with the field GPS continuous observation data,we roughly estimate the viscous coefficient of each layer. With the viscoelastic horizontal layer model,we calculate the viscoelastic co-seismic Coulomb stress change caused by the Yutian M_S7. 3 earthquakes 2008 and 2014 respectively. Based on the Coulomb stress change,using the calculation method of "direct "aftershock frequency,we come up with the theoretical earthquake frequency directly related to the mainshock and the co-seismic Coulomb stress change in the study area. Then we put forward a method,based on the comparison of theoretical and actual earthquake frequency or the comparison between theoretical and practical earthquake frequency-distance decay curve fitting residuals,to estimate the magnitude of a maximum sequent earthquake,directly related to the mainshock co-seismic Coulomb stress change. Results calculated by different methods show that the maximum follow-up earthquake magnitude caused by the coseismic Coulomb stress change lies from M_S7. 2 to M_S7. 5 following Yutian M_S7. 3 earthquake in 2008; but that of the 2014 Yutian M_S7. 3 earthquake is M_S6. 3. The former is very close to the Yutian M_S7. 3 earthquake in 2014.Because of the same magnitude,relatively close spatial distance,short time interval,the same region of the external force,the strong correlation between two seismic tectonic and a clear stress interaction,we thus consider that the two Yutian M_S7. 3 earthquakes in 2008 and 2014 constitute a pair of generalized double shock type earthquake. This is consistent with the sequence type characteristic of past "double shock"earthquakes in the region. In this paper,the influence of the magnitude lower limit and the b-value in the relationship of G-R on the results is discussed. As a result,when the viscoelastic coseismic Coulomb stress variation is determined,the lower limit of magnitude has little effect on the maximum sequent earthquake magnitude estimation,but b-value of G-R has a greater impact on the results.展开更多
In order to analyze the seismic brightness temperature anomalies associated with the Yutian earthquake which occurred at Yutian County, Xinjiang on February 12,2014, daily brightness temperature data was collected fro...In order to analyze the seismic brightness temperature anomalies associated with the Yutian earthquake which occurred at Yutian County, Xinjiang on February 12,2014, daily brightness temperature data was collected from the China Geostationary Meteorological Satellite FY-2E,for the period from May 1,2012 to April 30,2014 and the geographical extent of 30°- 45°N latitude and 70°- 95°E longitude. The continuous wavelet transform method was used to analyze the relative wavelet power spectrum( RWPS) of brightness temperature data for each pixel. And the RWPS time-spatial evolution within the analysis area was obtained. The results showed that the anomaly started to appear at the vicinity of epicentre since October 2013, and anomalous areas gradually enlarged and stretched towards to Altun fault zone and the eastern part of West Kunlun fault zone. Anomalies began to appear at fault zones at Middle Tianshan Mountains, Southern Tianshan Mountains and the western part of the West Kunlun Mountains area which is located at the western margin of Tarim basin,since November 2013. Then anomalous area further enlarged and gathered along fault zones,and eventually,anomalous belts were developed along fault zones around the Tarim basin. The anomaly area and amplitude reached their maximum in late December 2013 and early January 2014. With the impending earthquake,the anomaly area and amplitude dwindled. Anomalies at the vicinity of epicentre disappeared days before the occurrence of the main shock. However, the anomaly at Altun and Middle Tianshan areas still remained. After the main shock,the anomaly attenuated quickly and the whole anomaly disappeared in late February 2014.展开更多
We successfully employ an automatic centroid moment tensor(CMT) inversion system to infer the CMT solutions of the February 12,2014 MS7.3 Yutian,Xinjiang earthquake using near-field seismic waveforms(4° < △ &...We successfully employ an automatic centroid moment tensor(CMT) inversion system to infer the CMT solutions of the February 12,2014 MS7.3 Yutian,Xinjiang earthquake using near-field seismic waveforms(4° < △ < 12°) observed by the virtual China seismic networks,which have been recently set up.The results indicate that this event occurred on a rupture plane(strike 243°,dip 70°,and rake-18°),showing left-lateral strike-slip faulting with a minor normal-faulting component.The centroid in the horizontal direction is located nearly 13 km east of the epicenter(36.123° N,82.499° E),and the best-fitting centroid depth is around 10 km.The total scalar moment,M0,is retrieved with an average value of 3.05 × 1019N·m,corresponding to moment magnitude MW6.92.Most of the energy is released within about 14 s.Moreover,we discuss about the potential application of this system in earthquake disaster decision.展开更多
Since 2001, there have occurred in succession the 2001 Kunlun Mountains M S8. 1earthquake,the 2008 Wenchuan M S8. 0 earthquake,the 2010 Yushu M S7. 1 earthquake and the 2012 Lushan M S7. 0 earthquake in the periphery ...Since 2001, there have occurred in succession the 2001 Kunlun Mountains M S8. 1earthquake,the 2008 Wenchuan M S8. 0 earthquake,the 2010 Yushu M S7. 1 earthquake and the 2012 Lushan M S7. 0 earthquake in the periphery of the Bayan Har block. By comparison of the characteristics of seismic strain release variations before and after the Kunlun Mountains M S8. 1 earthquake in the same time length in the geodynamical related regions,we found that the seismic strain release was obviously enhanced after the earthquake in the Longmenshan area,Batang area,and the NS-trending valleys at the west of the Hot Spring Basin. The Wenchuan earthquake occurred in the first area,and the Yushu earthquake is related to the second area. After the earthquake rupture occurred on the East Kunlun fault zone on the northern boundary of the Bayan Har Block,crustal materials on the south side of the fault zone migrated to the southeast,leading to a concentration of tectonic deformation in the Longmenshan thrust belt, e ventually rupturing on the Longmenshan thrust belt. This earthquake case illustrates that seismicity enhancement zones are possibly prone to long-term destructive earthquakes. After the M S7. 3 earthquake in Yutian,Xinjiang on February 12,2014,earthquake frequency and seismic strain release markedly increased in the junction area between the eastern Qilian Mountain tectonic belt and the Altun Tagh fault zone,where more attention should be paid to the long-term seismic risk.展开更多
First of all,using the GPS velocity field from campaign GPS measurements implemented by CMONC( C hina Crustal Movement Observation) a nd TEONC( C hina Tectonic Environment Observation Networks) u p to 2013, w e analyz...First of all,using the GPS velocity field from campaign GPS measurements implemented by CMONC( C hina Crustal Movement Observation) a nd TEONC( C hina Tectonic Environment Observation Networks) u p to 2013, w e analyzed the background of regional crustal horizontal movement and deformation before the M S7. 3 Yutian,Xinjiang earthquake on February 12,2014. Then,by comparing this to the vertical movement from leveling measurements,we studied the crustal movement deformation and the state of strain accumulation on the northeastern edge of Qinghai-Tibetan block.Finally,we investigated the possible effects on the earthquake activity of the northeastern edge of Tibet from the M S7. 3 Yutian earthquake. The result indicates that,the M S7. 3Yutian earthquake occurred against the background of strong tectonic movement and intensive intracontinental crustal differential movement on the edges of tectonic blocks in western China,and also that it happened in the period of the strong tectonic stress field in Qinghai-Tibetan block and its edges. The sinistral strike-slip and stress transfer of the Yutian M S7. 3 earthquake may accelerate the rupture of fault segments with high strain accumulation at the northeastern edge of Qinghai-Tibetan block( especially in Qilian Mountain fault zone,and border area of Gansu,Qinghai and Sichuan provinces on the south of western Qinling).展开更多
This paper calculates the static Coulomb stress changes generated by four earthquakes in the Yutian area during 2008 ~ 2014 separately,then discusses the triggering influence,their accumulated Coulomb stress changes a...This paper calculates the static Coulomb stress changes generated by four earthquakes in the Yutian area during 2008 ~ 2014 separately,then discusses the triggering influence,their accumulated Coulomb stress changes and their influence on nearby faults.The results indicate that the M S5.5 earthquake in 2011 and the M_S7.3 earthquake in 2014 are both in the regions where the Coulomb stress change is positive,the stress changes are 0.004 MPa and 0.021 MPa, respectively, meaning they are triggered by prior earthquakes.The M S6.2 earthquake in 2012 occurred in the place where Coulomb stress change was negative,so it is postponed by the prior earthquakes.The image of Coulomb stress changes of the M S7.3 earthquake in 2014 is in accord with aftershocks( M L≥ 3.0)distribution,but some regions on the fault where the Coulomb stress change is positive have few aftershocks,and strong aftershocks may occur at these districts in future.In addition,this paper calculates the Coulomb stress change on nearby faults,and finds that the Coulomb stress changes of different elements in the GGC fault are very different,and must receive strong triggered-influence,though the result may be influenced by the input finite fault model,so there is still a large earthquake-risk.The GGN,PLC,PLW and LBW faults were also triggered by the four earthquakes occurring between 2008 ~ 2014.Their maximum Coulomb stress changes all exceed 0.002 MPa,so they also have a strong earthquake hazard.展开更多
基金supported by the National Natural Science Foundation of China(40574012)
文摘Based on the data of the repeated gravity observation network in Chinese mainland since 1998, we analyzed the temporal changes of regional gravity field before the 2008 Yutian Ms7.3 earthquake. The result shows some mid-to-long term (two to ten years) changes during the earthquake' s preparation. Notable fea- tures are a gravity increase lasting several years and a relatively large-scaled gradient zone of gravity change, the former indicating a continuous energy accumulation and the latter a possible location of seismic rupture. These gravity changes showed a trend of increase-accelerated increase-decelerated increase, similar to that of the Tangshan Ms7.8 earthquake in 1976. The maximum accumulated gravity change related to the earthquake reached 200 × 10 -8 ms -2.
基金supported by the Spark Progoram of Earthquake Science(XH13037Y)Earthquake Tracking(2014010203)the National Natural Science Fourdation of China(41372215,41272233,41174004)
文摘Based on analysis of the GPS data during 1999-2007,2009-2011,and 2011-2013 mainly from the Crustal Motion Observation Network of China,we obtained the GPS horizontal velocity field,the GPS strain rate field,and the profiles across the southwestern segment of the Altyn Tagh Fault zone and its adjacent regions and identified the different characteristics of horizontal crustal deformation fields and profiles during different periods. The results show that,before the February 12,2014,Ms7. 3 Yutian earthquake,the laevorotation deformation along the southwestern segment of the Altyn Tagh Fault zone increased about 3. 3 mm /a during 2011-2013,relative to that in 2009-2011,and the GPS strain rate field distributed in the southeastern segment of the Altyn Tagh Fault during 2011-2013 increased obviously. These abnormal changes may be regarded as precursors to the Ms7. 3 Yutian earthquake.
基金funded jointly by Foundation of Earthquake Administration of Xinjiang Uygur Autonomous Region(Grant No.201401)the Contract for Annual Earthquake Situation Tracking Task of 2014,CEA(2014020106)
文摘The paper inverts the focal mechanism solutions of the Yutian M_S7. 3 main shock,foreshocks and M_S≥3. 5 aftershocks by using the CAP method,based on the broadband waveforms recorded by the Xinjiang and Tibet Digital Seismic Networks. The results show that the M_S7. 3 strong earthquake is of strike-slip type with a normal faulting component,and combined with the analysis of focal structure and the aftershock distribution,the nodal plane I with strike 241°,dip 90° and rake- 22° is considered to be the seismogenic fault plane of the main shock. The direction of P-axis for the main shock is 194°,close to the near NS direction of the principal stress P-axis of historical strong earthquakes in this region. The focal mechanism solution of the M_S5. 4 foreshock has a good consistency with that of the main shock. Among the 18 aftershocks,10 are of strike-slip type,6 are of normal faulting type and 2 are of thrust type. 70% of the aftershocks in the sequence have a focal mechanism with P-axis in the near-NS direction. The focal depths of this M_S7. 3 earthquake sequences are distributed in the range of 5km- 28 km,with the majority in the depth range of 15km- 20 km,slightly deeper than the depth of 10 km of the main shock as calculated.
基金jointly sponsored by the National Key Technology R&D Program of China(2012BAK19B04-01-05)the Youth Earthquake Situation Tracking Program of China Earthquake Administration(2015010106)
文摘The M_S7. 3 earthquake occurred in Yutian,Xinjiang on February 12,2014. Based on seismic waveform data before the earthquake and aftershocks of the earthquake sequence,which were recorded by the Xinjiang Regional Digital Seismic Network, this paper corrected instrument response,propagation path and site response of the S-wave recording spectra. We then calculated with genetic algorithms,on the basis of the Brune model,the source parameters of the 102 M_L≥3. 0 Yutian earthquake sequence,seismic moment,apparent stress and corner frequency. The results show that,seismic moment of the earthquake sequence is between 3. 46 × 10~11- 2. 08 × 10~15N·m,apparent stress is between1. 48 × 10~5- 1. 16 × 10~6 Pa,mean stress level is 0. 31 MPa,and corner frequency is between1. 4- 7. 1Hz in the range of 3. 0- 5. 0. By analyzing the apparent stress and corner frequency variation with time,we obtain that apparent stress of earthquakes before the Yutian M_S7. 3 earthquake was significantly higher than the aftershock sequence,but the corner frequency was significantly lower than the aftershock sequence. Apparent stress was at a high level before the main shock, which shows that the main shock zone accumulated higher stress,and then the apparent stress was reduced. The main shock occurred in the process of slow increase. Because of the release of a large amount of stress,after the M_S7. 3 earthquake,the apparent stress was gradually reduced. That was the performance of low stress fracture of aftershocks.
基金founded the Projects of Science for Earthquake Resilience(XH16042Y)Project of Earthquake Science Foundation of Xinjiang,China(201501,201514)
文摘After the Yutian M_S7.3 earthquake,the authors instantly collected 1Hz high frequency data of the 4 reference stations within 350 km around the epicenter,and calculated the GNSS data with the TRACK module. The results showed that:( 1) The co-seismic displacement of Yutian station,about 54 km from the epicenter,is the most obvious,particularly in the EW component,with a change of about 52.5 ± 11mm,which is more than three times the mean-square error of calculating precision.( 2) In the Yutian reference station,the biggest variation in the EW component appeared within 1 minute after the earthquake.( 3) The change in the NS component is not great.
基金supported by the National Basic Research Program of China(2013CB733302)the National Natural Science Foundation of China(41374009)+1 种基金the Public Benefit Scientific Research Project of China(201412001)the Natural Science Foundation of Shandong Province,China(ZR2013DM009)
文摘On February 12,2014,a large Mw7. 3 earthquake occurred in Yutian of Xijiang Province,China.We processed the global ionosphere maps provided by CODE( the Center for Orbit Determination in Europe)and the foF2( the critical frequency of F2-layer) data of Chongqing ionosonde station to analyze the preearthquake ionospheric anomalies. Solar activities and magnetic storm were checked by the sliding inter quartile range method to remove their effects on the ionosphere. A positive ionospheric anomaly with the large amplitude of 20 TECU was observed near the epicenter on February 3( 10th day before the earthquake). In addition,the foF2 at Chongqing station had an unusual increase of more than 40% on the day,which was consistent with the TEC( Total Electron Content) anomaly. The global disturbance represents that the peak of TEC anomaly didn’t coincide with the vertical projection of epicenter. The TEC anomalous area was closer to the equator,and it mainly occurred from local time 16 ∶ 00 to 20 ∶ 00. An enhancement of TEC with the small amplitude also appeared in the magnetically conjugated region.
基金Basic Research program from the Institute of Earthquake Forecasting, China Earthquake Administration(Grant No. 2021IEF0505, CEAIEF20220102, and CEAIEF2022050502)high-resolution seismic monitoring and emergency application demonstration (phase Ⅱ)(Grant No. 31-Y30F09-9001-20/22)+1 种基金the National Natural Science Foundation of China (Grant No. 42072248 and 42041006)the National Key Research and Development Program of China (Grant No. 2021YFC3000601-3 and 2019YFE0108900).
文摘Earthquake-triggered liquefaction deformation could lead to severe infrastructure damage and associated casualties and property damage.At present,there are few studies on the rapid extraction of liquefaction pits based on high-resolution satellite images.Therefore,we provide a framework for extracting liquefaction pits based on a case-based reasoning method.Furthermore,five covariates selection methods were used to filter the 11 covariates that were generated from high-resolution satellite images and digital elevation models(DEM).The proposed method was trained with 450 typical samples which were collected based on visual interpretation,then used the trained case-based reasoning method to identify the liquefaction pits in the whole study area.The performance of the proposed methods was evaluated from three aspects,the prediction accuracies of liquefaction pits based on the validation samples by kappa index,the comparison between the pre-and post-earthquake images,the rationality of spatial distribution of liquefaction pits.The final result shows the importance of covariates ranked by different methods could be different.However,the most important of covariates is consistent.When selecting five most important covariates,the value of kappa index could be about 96%.There also exist clear differences between the pre-and post-earthquake areas that were identified as liquefaction pits.The predicted spatial distribution of liquefaction is also consistent with the formation principle of liquefaction.
基金supported by the National Natural Science Foundation of China ( 41404045)the Earthquake Tracing Task of China Earthquake Administration(2014020412)
文摘The February 12,2014,MS7.3,earthquake in Yutian,Xinjiang,China,occurred as a result of shallow strike-slip faulting in the tectonically complex region of the northern Tibetan Plateau,with a depth of 17 km.This earthquake occurred several hundred kilometers north of the convergent India-Eurasia plate boundary.The epicenter location of the Yutian earthquake,36.1° N,82.5° E,is 110 km north of Yutian County,Hotan Prefecture.A large number of aftershocks from ML2.0 to ML3.0 occurred until 12:00oclock,February 23,2014 and the largest aftershock,MS5.7,occurred at 17:24 p.m.,February 12,2014.The b and h value of Yutian sequence are 0.70 and 1.29,respectively.The waiting time method reveals that the strong aftershocks above ML4.5comply with a linear relationship,which is consistent with the characteristics of a mainshock-aftershock sequence.Furthermore,we calculate the source parameters and analyze the rupture process based on the empirical relationships for the Yutian earthquake,and the results indicate a frictional undershoot behavior in the dynamic source process of the Yutian earthquake,which is also in agreement with the lower and similar b values compared with the 2008 MS7.3 Yutian earthquake and the 2012 MS6.2 Yutian earthquake.
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funded by the Open-end Foundation of State Key Laboratory of Earthquake Dynamics(LED2014B01)Project of Earthquake Science Foundation of Xinjiang,China(20120201)
文摘The basic parameters,seismogenic structure and seismic sequences characteristics of the Yutian MS7. 3 earthquake on February 12,2014 are introduced and compared to the Yutian MS7. 3 earthquake in 2008. The results show that the MS5. 4 earthquake is regarded as an immediate foreshock of the Yutian MS7. 3 main shock. The frequency of strong aftershock sequences was low and their number declined quickly,and the maximum aftershock was a MS5. 7 earthquake. According to analysis of the historical earthquake sequence type,and parameter of h-value,b-value and energy release ratio between main shock and sequence etc.,we found the preliminary conclusion that the Yutian MS7. 3 earthquake sequence in 2014 was a foreshock-main shock-aftershock type.
基金sponsored by the Scientific Research Fund of the Department of Earthquake Monitoring and Prediction,CEA
文摘On the basis of the previous studies of the layered crustal model in the Yutian area,combined with the field GPS continuous observation data,we roughly estimate the viscous coefficient of each layer. With the viscoelastic horizontal layer model,we calculate the viscoelastic co-seismic Coulomb stress change caused by the Yutian M_S7. 3 earthquakes 2008 and 2014 respectively. Based on the Coulomb stress change,using the calculation method of "direct "aftershock frequency,we come up with the theoretical earthquake frequency directly related to the mainshock and the co-seismic Coulomb stress change in the study area. Then we put forward a method,based on the comparison of theoretical and actual earthquake frequency or the comparison between theoretical and practical earthquake frequency-distance decay curve fitting residuals,to estimate the magnitude of a maximum sequent earthquake,directly related to the mainshock co-seismic Coulomb stress change. Results calculated by different methods show that the maximum follow-up earthquake magnitude caused by the coseismic Coulomb stress change lies from M_S7. 2 to M_S7. 5 following Yutian M_S7. 3 earthquake in 2008; but that of the 2014 Yutian M_S7. 3 earthquake is M_S6. 3. The former is very close to the Yutian M_S7. 3 earthquake in 2014.Because of the same magnitude,relatively close spatial distance,short time interval,the same region of the external force,the strong correlation between two seismic tectonic and a clear stress interaction,we thus consider that the two Yutian M_S7. 3 earthquakes in 2008 and 2014 constitute a pair of generalized double shock type earthquake. This is consistent with the sequence type characteristic of past "double shock"earthquakes in the region. In this paper,the influence of the magnitude lower limit and the b-value in the relationship of G-R on the results is discussed. As a result,when the viscoelastic coseismic Coulomb stress variation is determined,the lower limit of magnitude has little effect on the maximum sequent earthquake magnitude estimation,but b-value of G-R has a greater impact on the results.
基金funded by the National Natural Science Foundation of China(41204057)Seismic Situation Tracking Project of China Earthquake Administration(20150401)
文摘In order to analyze the seismic brightness temperature anomalies associated with the Yutian earthquake which occurred at Yutian County, Xinjiang on February 12,2014, daily brightness temperature data was collected from the China Geostationary Meteorological Satellite FY-2E,for the period from May 1,2012 to April 30,2014 and the geographical extent of 30°- 45°N latitude and 70°- 95°E longitude. The continuous wavelet transform method was used to analyze the relative wavelet power spectrum( RWPS) of brightness temperature data for each pixel. And the RWPS time-spatial evolution within the analysis area was obtained. The results showed that the anomaly started to appear at the vicinity of epicentre since October 2013, and anomalous areas gradually enlarged and stretched towards to Altun fault zone and the eastern part of West Kunlun fault zone. Anomalies began to appear at fault zones at Middle Tianshan Mountains, Southern Tianshan Mountains and the western part of the West Kunlun Mountains area which is located at the western margin of Tarim basin,since November 2013. Then anomalous area further enlarged and gathered along fault zones,and eventually,anomalous belts were developed along fault zones around the Tarim basin. The anomaly area and amplitude reached their maximum in late December 2013 and early January 2014. With the impending earthquake,the anomaly area and amplitude dwindled. Anomalies at the vicinity of epicentre disappeared days before the occurrence of the main shock. However, the anomaly at Altun and Middle Tianshan areas still remained. After the main shock,the anomaly attenuated quickly and the whole anomaly disappeared in late February 2014.
基金funded by Special Oceanic Scientific Research Program(201405026)Science for Earthquake Resilience Program(XH12060Y)Special Seismological Industry Research Program(201208003)
文摘We successfully employ an automatic centroid moment tensor(CMT) inversion system to infer the CMT solutions of the February 12,2014 MS7.3 Yutian,Xinjiang earthquake using near-field seismic waveforms(4° < △ < 12°) observed by the virtual China seismic networks,which have been recently set up.The results indicate that this event occurred on a rupture plane(strike 243°,dip 70°,and rake-18°),showing left-lateral strike-slip faulting with a minor normal-faulting component.The centroid in the horizontal direction is located nearly 13 km east of the epicenter(36.123° N,82.499° E),and the best-fitting centroid depth is around 10 km.The total scalar moment,M0,is retrieved with an average value of 3.05 × 1019N·m,corresponding to moment magnitude MW6.92.Most of the energy is released within about 14 s.Moreover,we discuss about the potential application of this system in earthquake disaster decision.
基金jointly supported by National Science Foundation of China(41302171)Active Fault Exploration in China(60112304)Basic Scientific Research Funds of China Earthquake Administration(2014IES0401,2012IES010303)
文摘Since 2001, there have occurred in succession the 2001 Kunlun Mountains M S8. 1earthquake,the 2008 Wenchuan M S8. 0 earthquake,the 2010 Yushu M S7. 1 earthquake and the 2012 Lushan M S7. 0 earthquake in the periphery of the Bayan Har block. By comparison of the characteristics of seismic strain release variations before and after the Kunlun Mountains M S8. 1 earthquake in the same time length in the geodynamical related regions,we found that the seismic strain release was obviously enhanced after the earthquake in the Longmenshan area,Batang area,and the NS-trending valleys at the west of the Hot Spring Basin. The Wenchuan earthquake occurred in the first area,and the Yushu earthquake is related to the second area. After the earthquake rupture occurred on the East Kunlun fault zone on the northern boundary of the Bayan Har Block,crustal materials on the south side of the fault zone migrated to the southeast,leading to a concentration of tectonic deformation in the Longmenshan thrust belt, e ventually rupturing on the Longmenshan thrust belt. This earthquake case illustrates that seismicity enhancement zones are possibly prone to long-term destructive earthquakes. After the M S7. 3 earthquake in Yutian,Xinjiang on February 12,2014,earthquake frequency and seismic strain release markedly increased in the junction area between the eastern Qilian Mountain tectonic belt and the Altun Tagh fault zone,where more attention should be paid to the long-term seismic risk.
基金sponsored by the Special Found for the Earthquake Scientific Research of China(201208009)the Earthquake Forecast and Prediction System Program of China Earthquake Administration in 2014
文摘First of all,using the GPS velocity field from campaign GPS measurements implemented by CMONC( C hina Crustal Movement Observation) a nd TEONC( C hina Tectonic Environment Observation Networks) u p to 2013, w e analyzed the background of regional crustal horizontal movement and deformation before the M S7. 3 Yutian,Xinjiang earthquake on February 12,2014. Then,by comparing this to the vertical movement from leveling measurements,we studied the crustal movement deformation and the state of strain accumulation on the northeastern edge of Qinghai-Tibetan block.Finally,we investigated the possible effects on the earthquake activity of the northeastern edge of Tibet from the M S7. 3 Yutian earthquake. The result indicates that,the M S7. 3Yutian earthquake occurred against the background of strong tectonic movement and intensive intracontinental crustal differential movement on the edges of tectonic blocks in western China,and also that it happened in the period of the strong tectonic stress field in Qinghai-Tibetan block and its edges. The sinistral strike-slip and stress transfer of the Yutian M S7. 3 earthquake may accelerate the rupture of fault segments with high strain accumulation at the northeastern edge of Qinghai-Tibetan block( especially in Qilian Mountain fault zone,and border area of Gansu,Qinghai and Sichuan provinces on the south of western Qinling).
基金funded by the National Key Technology R&D Program of China(2012BAK19B02)
文摘This paper calculates the static Coulomb stress changes generated by four earthquakes in the Yutian area during 2008 ~ 2014 separately,then discusses the triggering influence,their accumulated Coulomb stress changes and their influence on nearby faults.The results indicate that the M S5.5 earthquake in 2011 and the M_S7.3 earthquake in 2014 are both in the regions where the Coulomb stress change is positive,the stress changes are 0.004 MPa and 0.021 MPa, respectively, meaning they are triggered by prior earthquakes.The M S6.2 earthquake in 2012 occurred in the place where Coulomb stress change was negative,so it is postponed by the prior earthquakes.The image of Coulomb stress changes of the M S7.3 earthquake in 2014 is in accord with aftershocks( M L≥ 3.0)distribution,but some regions on the fault where the Coulomb stress change is positive have few aftershocks,and strong aftershocks may occur at these districts in future.In addition,this paper calculates the Coulomb stress change on nearby faults,and finds that the Coulomb stress changes of different elements in the GGC fault are very different,and must receive strong triggered-influence,though the result may be influenced by the input finite fault model,so there is still a large earthquake-risk.The GGN,PLC,PLW and LBW faults were also triggered by the four earthquakes occurring between 2008 ~ 2014.Their maximum Coulomb stress changes all exceed 0.002 MPa,so they also have a strong earthquake hazard.