The temporal and spatial variations of surface latent heat flux (SLHF) before and after the Mw9.0 earthquake that occurred on the west coast of Sumatra, Indonesia on 26 December 2004 are summarized. It is found that b...The temporal and spatial variations of surface latent heat flux (SLHF) before and after the Mw9.0 earthquake that occurred on the west coast of Sumatra, Indonesia on 26 December 2004 are summarized. It is found that before the earthquake significant SLHF anomalies occurred at the epicentral area and its vicinity. The largest SLHF anomaly oc- curred on the subduction zone in the middle part of Burma micro-plate, where the middle part of the rup- ture zone is located and the aftershocks are concen- trated. The developments of the anomaly involved growing of the anomaly from small to large and spreading of the anomaly from disordered to con- centrated. The anomaly began to occur on the east extensional boundary of the Burma micro-plate and its adjacent oceanic basin, and then propagated to the west compressive boundary, where the subduc- tion zone exists. Finally, the anomaly disappeared after the main shock. The seismic source is consid- ered to be a dissipation system. The increase of stress prior to an earthquake may enhance the ex- change of energy and material between the seismic source system and the outer system, resulting in the increase of the rate of energy exchange between sea surface and atmosphere, which is believed to be the main reason of the generation of SLHF anomaly.展开更多
利用中国大陆GPS连续站观测数据,根据电离层单层模型,计算得到中国大陆上空电离层电子总含量TEC（Total Electron Content）值的时间序列。选取2001—2008年发生在中国大陆地区的11个MS≥6.0地震,分析了这11个地震前后TEC值时间序列的...利用中国大陆GPS连续站观测数据,根据电离层单层模型,计算得到中国大陆上空电离层电子总含量TEC（Total Electron Content）值的时间序列。选取2001—2008年发生在中国大陆地区的11个MS≥6.0地震,分析了这11个地震前后TEC值时间序列的变化特征。分析结果显示,地震活动期间距离震中700 km以外的GPS连续观测站上空TEC值的异常现象不明显,TEC值变化基本在0.5 TECU之内。11个震例中有6个震例TEC值出现了负异常现象,主要表现在震前1~5 d,并且观测站距离震中越近,TEC值变化越明显,少数震例在地震发生期间TEC值明显增加。研究认为,利用GPS连续观测数据研究与地震有关的电离层前兆是可能的。展开更多
An Ms6.4 earthquake occurred in the Menyuan county of Qinghai Province on Jan 21, 2016. In order to recognize the development of horizontal deformation and distinguish precursory deformation anomalies, we obtained coo...An Ms6.4 earthquake occurred in the Menyuan county of Qinghai Province on Jan 21, 2016. In order to recognize the development of horizontal deformation and distinguish precursory deformation anomalies, we obtained coordinates time series, velocity and strain model around the seismic zones from processing of continuous observations from 2010 and 6 times of surveying Global Positioning System （GPS） data since 2009. The results show that, before the earthquake, the eastern segmentation of the Qilian tectonic zone where the Lenglongling Fault located is in strong crustal shortening and compressional strain state with dilatational rates of -15 to -25 ppb. The Lenglongling Fault has a strike-slip rate of 3.1 mm/a and a far-field differential orthogonal rate of 7 mm/a, while differential rate is only 1.2 mm/a near the fault, which reflects its locking feature with strain energy accumulation and high seismic risks. Dynamic evolution of deformation model shows that preevent dilatational rates around the seismic zones increases from 15 ppb/a to -20 ppb/a with its center moving to the source areas. Time series of N components of G337 station, which is 13.7 km away from the Lenglongling Fault, exhibit a 5 mm/a acceleration anomaly. Time series of base-station QHME （in Menyuan） displays a reverse acceleration from the end of Sep. to Dec., 2016 when it comes to a largest deviation, and the accumulative displacement is more than 4 mm and the value reverse till the earthquake. In our results, coseismic displacement of N, E, U components in QHME site are 3.0 mm, 3.0 mm, -5.4 mm, respectively. If we profile these values onto the Lenglongling Fault, we can achieve a 1.1 mm of strike slip and 4.1 mm updip slip relative to the hanging wall.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.40372131)the Key Projects Required by National 10th Five-year Plan(Grant No.2004BA601B01-02-02)the National High-tech"863"Project(Grant No.2003AA134060).
文摘The temporal and spatial variations of surface latent heat flux (SLHF) before and after the Mw9.0 earthquake that occurred on the west coast of Sumatra, Indonesia on 26 December 2004 are summarized. It is found that before the earthquake significant SLHF anomalies occurred at the epicentral area and its vicinity. The largest SLHF anomaly oc- curred on the subduction zone in the middle part of Burma micro-plate, where the middle part of the rup- ture zone is located and the aftershocks are concen- trated. The developments of the anomaly involved growing of the anomaly from small to large and spreading of the anomaly from disordered to con- centrated. The anomaly began to occur on the east extensional boundary of the Burma micro-plate and its adjacent oceanic basin, and then propagated to the west compressive boundary, where the subduc- tion zone exists. Finally, the anomaly disappeared after the main shock. The seismic source is consid- ered to be a dissipation system. The increase of stress prior to an earthquake may enhance the ex- change of energy and material between the seismic source system and the outer system, resulting in the increase of the rate of energy exchange between sea surface and atmosphere, which is believed to be the main reason of the generation of SLHF anomaly.
基金support by National Natural Science Foundation of China(51479163,41174083)
文摘An Ms6.4 earthquake occurred in the Menyuan county of Qinghai Province on Jan 21, 2016. In order to recognize the development of horizontal deformation and distinguish precursory deformation anomalies, we obtained coordinates time series, velocity and strain model around the seismic zones from processing of continuous observations from 2010 and 6 times of surveying Global Positioning System （GPS） data since 2009. The results show that, before the earthquake, the eastern segmentation of the Qilian tectonic zone where the Lenglongling Fault located is in strong crustal shortening and compressional strain state with dilatational rates of -15 to -25 ppb. The Lenglongling Fault has a strike-slip rate of 3.1 mm/a and a far-field differential orthogonal rate of 7 mm/a, while differential rate is only 1.2 mm/a near the fault, which reflects its locking feature with strain energy accumulation and high seismic risks. Dynamic evolution of deformation model shows that preevent dilatational rates around the seismic zones increases from 15 ppb/a to -20 ppb/a with its center moving to the source areas. Time series of N components of G337 station, which is 13.7 km away from the Lenglongling Fault, exhibit a 5 mm/a acceleration anomaly. Time series of base-station QHME （in Menyuan） displays a reverse acceleration from the end of Sep. to Dec., 2016 when it comes to a largest deviation, and the accumulative displacement is more than 4 mm and the value reverse till the earthquake. In our results, coseismic displacement of N, E, U components in QHME site are 3.0 mm, 3.0 mm, -5.4 mm, respectively. If we profile these values onto the Lenglongling Fault, we can achieve a 1.1 mm of strike slip and 4.1 mm updip slip relative to the hanging wall.
