During the earthquake in Emilia（Italy） of 2012,ca.30 permanent GPS stations were in operation within a radius of about 100 km from the epicenter,each equipped with an antenna rigidly fixed to the host building and s...During the earthquake in Emilia（Italy） of 2012,ca.30 permanent GPS stations were in operation within a radius of about 100 km from the epicenter,each equipped with an antenna rigidly fixed to the host building and sampling the GPS signal at a high rate（〉 1 Hz）.From the recording of the GPS measurements,the instantaneous displacements s（t） in the NorthSouth and East-West directions of the phase centers of the single GPS antennas at each permanent station during the most important seismic sequences were calculated in kinematic mode.Subsequently,for each of the two displacements considered as two distinct external forces,the elastic response spectra of the building were determined and from them the two periods of vibration T along two orthogonal directions coinciding with the walls of the building were extracted.The experimentally obtained periods of vibration were compared with those inferable from the technical literature.In this way,a sufficiently large sample was obtained per building type,geometry（square,rectangular,regular or irregular planimetry）,height（from a minimum of 4 to a maximum of 20 m） and materials（masonry,reinforced concrete,etc.）.From the computational point of view,the study confirmed that GPS is an emerging tool for monitoring dynamic displacements and the experimentally estimated value of T is always lower than the one estimated with the formulae reported in the literature.The limitations of the study lie in the impossibility to choose a priori the geometry and/or structural type of the building hosting the GPS station.展开更多
TEQC is used to check the observations quality of 173 GPS campaign stations in the Northeast and North China. Each station was observed with an occupation of 4 days. The quality of the 692 data files is analyzed by th...TEQC is used to check the observations quality of 173 GPS campaign stations in the Northeast and North China. Each station was observed with an occupation of 4 days. The quality of the 692 data files is analyzed by the ratio of overall observations to possible observations, MP1, MP2 and the ratio of observations to slips. The reasons for multipath and cycle slips can be derived from the photos taken in the field. The results show that the coverage of trees and buildings/structures, and the interference of high-voltage power lines near the stations are the main reasons. In a small area, the horizontal velocity field in the period 2011-2013 is exemplified, where the magnitudes and directions of the 4 stations＇ rates are clearly different with that of other stations. It seems that the error caused by the worse environment cannot be mitigated through post processing. Therefore, these conclusions can help the establishment of GNSS stations, measurements, data processing and formulating standards in future.展开更多
Wanshan area has been chosen to be the specified field to calibrate and validate(Cal/Val)the HY-2 altimeter and its follow-on satellites.In March 2018,an experiment has been conducted to determine the sea surface heig...Wanshan area has been chosen to be the specified field to calibrate and validate(Cal/Val)the HY-2 altimeter and its follow-on satellites.In March 2018,an experiment has been conducted to determine the sea surface height(SSH)under the HY-2 A ground track(Pass No.203).A GPS towing-body(GPS-TB)was designed to measure the SSH covering an area of about 6 km×28 km wide centered on the HY-2 A altimeter satellite ground track.Three GPS reference stations,one tide gauge and a GPS buoy were placed in the research area,in order to process and resolve the kinematic solution and check the precision of the GPS-TB respectively.All the GPS data were calculated by the GAMIT/GLOBK software and TRACK module.The sea surface was determined by the GPS-TB solution and the tide gauge placed on Zhiwan Island.Then the sea surface of this area was interpolated by Arc GIS10.2 with ordinary Kriging method.The results showed that the precision of the GPS-TB is about 1.10 cm compared with the tide gauge placed nearby,which has an equivalent precision with the GPS buoy.The interpolated sea surface has a bias of–1.5–4.0 cm with standard deviation of 0.2–2.4 cm compared with the checking line.The gradient of the measured sea surface is about 1.62 cm/km along the HY-2 orbit which shows a good agreement compared with the CLS11 mean sea surface(MSS).In the Cal/Val of satellites,the sea surface between the tide gauge/GPS buoy and the footprint of altimeter can be improved by this work.展开更多
In order to study the characteristics of crustal deformation around the epicenter before the 2016 M_S6. 4 Menyuan earthquake,the GPS continuous stations of the period from 2010 to 2016 were selected according to the o...In order to study the characteristics of crustal deformation around the epicenter before the 2016 M_S6. 4 Menyuan earthquake,the GPS continuous stations of the period from 2010 to 2016 were selected according to the observation data of the tectonic environment monitoring network in Chinese Mainland. The deformation characteristics of the crust before the earthquake were discussed through inter-station baseline time series analysis and the strain time series analysis in the epicentral region. The results show that a trend turn of the baseline movement state around the epicenter region occurred after 2014,and the movement after 2014 reflects an obvious decreasing trend of compressional deformation.During this period,the stress field energy was in a certain accumulation state. Since the beginning of 2014,the EW-component linear strain and surface strain rate weakened gradually before the earthquake. It shows that there was an obvious deformation deficit at the epicentral area in the past two years,which indicates that the region accumulated a high degree of strain energy before the earthquake. Therefore,there was a significant background change in the area before the earthquake. The results of the study can provide basic research data for understanding the seismogenic process and mechanism of this earthquake.展开更多
To study the crustal movement in the vicinity of the epicenter before the Zhangye MS5.0 earthquake in 2019, the characteristics of crustal deformation before the earthquake are discussed through the GPS velocity field...To study the crustal movement in the vicinity of the epicenter before the Zhangye MS5.0 earthquake in 2019, the characteristics of crustal deformation before the earthquake are discussed through the GPS velocity field analysis based on the CMONOC data observed from GPS. The baseline time series between two continuous GPS stations and the strain time series of an area among several stations are analyzed in the epicenter area. The resulting time series of baseline azimuth around the epicenter reflects that the energy of the fault in the northern margin of Qilian Mountain is accumulated continuously before 2017. Besides,the movement trend of azimuth slows down after 2017,indicating the stress accumulation on both sides of the seismogenic fault zone has reached a certain degree. The first shear strain and EWdirection linear strain in the epicentral area of the Zhangye MS5.0 earthquake remain steady after 2017,and the surface strain rate decreases gradually after 2016. It is illustrated that there is an obvious deformation loss at the epicentral region three years before the earthquake,indicating that a certain degree of strain energy is accumulated in this area before the earthquake.展开更多
文摘During the earthquake in Emilia（Italy） of 2012,ca.30 permanent GPS stations were in operation within a radius of about 100 km from the epicenter,each equipped with an antenna rigidly fixed to the host building and sampling the GPS signal at a high rate（〉 1 Hz）.From the recording of the GPS measurements,the instantaneous displacements s（t） in the NorthSouth and East-West directions of the phase centers of the single GPS antennas at each permanent station during the most important seismic sequences were calculated in kinematic mode.Subsequently,for each of the two displacements considered as two distinct external forces,the elastic response spectra of the building were determined and from them the two periods of vibration T along two orthogonal directions coinciding with the walls of the building were extracted.The experimentally obtained periods of vibration were compared with those inferable from the technical literature.In this way,a sufficiently large sample was obtained per building type,geometry（square,rectangular,regular or irregular planimetry）,height（from a minimum of 4 to a maximum of 20 m） and materials（masonry,reinforced concrete,etc.）.From the computational point of view,the study confirmed that GPS is an emerging tool for monitoring dynamic displacements and the experimentally estimated value of T is always lower than the one estimated with the formulae reported in the literature.The limitations of the study lie in the impossibility to choose a priori the geometry and/or structural type of the building hosting the GPS station.
基金supported by the China National Special Fund for Earthquake Scientific Research(201508003,201508009)
文摘TEQC is used to check the observations quality of 173 GPS campaign stations in the Northeast and North China. Each station was observed with an occupation of 4 days. The quality of the 692 data files is analyzed by the ratio of overall observations to possible observations, MP1, MP2 and the ratio of observations to slips. The reasons for multipath and cycle slips can be derived from the photos taken in the field. The results show that the coverage of trees and buildings/structures, and the interference of high-voltage power lines near the stations are the main reasons. In a small area, the horizontal velocity field in the period 2011-2013 is exemplified, where the magnitudes and directions of the 4 stations＇ rates are clearly different with that of other stations. It seems that the error caused by the worse environment cannot be mitigated through post processing. Therefore, these conclusions can help the establishment of GNSS stations, measurements, data processing and formulating standards in future.
基金The National Key R&D Program of China under contract No.2018YFB0504900the National Natural Science Foundation of China under contract Nos 41406204 and 41501417Operational Support Service System For Natural Resources Satellite Remote Sensing。
文摘Wanshan area has been chosen to be the specified field to calibrate and validate(Cal/Val)the HY-2 altimeter and its follow-on satellites.In March 2018,an experiment has been conducted to determine the sea surface height(SSH)under the HY-2 A ground track(Pass No.203).A GPS towing-body(GPS-TB)was designed to measure the SSH covering an area of about 6 km×28 km wide centered on the HY-2 A altimeter satellite ground track.Three GPS reference stations,one tide gauge and a GPS buoy were placed in the research area,in order to process and resolve the kinematic solution and check the precision of the GPS-TB respectively.All the GPS data were calculated by the GAMIT/GLOBK software and TRACK module.The sea surface was determined by the GPS-TB solution and the tide gauge placed on Zhiwan Island.Then the sea surface of this area was interpolated by Arc GIS10.2 with ordinary Kriging method.The results showed that the precision of the GPS-TB is about 1.10 cm compared with the tide gauge placed nearby,which has an equivalent precision with the GPS buoy.The interpolated sea surface has a bias of–1.5–4.0 cm with standard deviation of 0.2–2.4 cm compared with the checking line.The gradient of the measured sea surface is about 1.62 cm/km along the HY-2 orbit which shows a good agreement compared with the CLS11 mean sea surface(MSS).In the Cal/Val of satellites,the sea surface between the tide gauge/GPS buoy and the footprint of altimeter can be improved by this work.
基金funded by the Earthquake Science and Technology Development Fund of GEA(Grant No.2016M02,2016Y02)the Earthquake Tracking Task of CEA(2017010221)+1 种基金the Fund of Science for Earthquake Resilience,CEA,(XH16038Y,XH14049)Grant of National Natural Science Foundation of China(51408567,41304048)
文摘In order to study the characteristics of crustal deformation around the epicenter before the 2016 M_S6. 4 Menyuan earthquake,the GPS continuous stations of the period from 2010 to 2016 were selected according to the observation data of the tectonic environment monitoring network in Chinese Mainland. The deformation characteristics of the crust before the earthquake were discussed through inter-station baseline time series analysis and the strain time series analysis in the epicentral region. The results show that a trend turn of the baseline movement state around the epicenter region occurred after 2014,and the movement after 2014 reflects an obvious decreasing trend of compressional deformation.During this period,the stress field energy was in a certain accumulation state. Since the beginning of 2014,the EW-component linear strain and surface strain rate weakened gradually before the earthquake. It shows that there was an obvious deformation deficit at the epicentral area in the past two years,which indicates that the region accumulated a high degree of strain energy before the earthquake. Therefore,there was a significant background change in the area before the earthquake. The results of the study can provide basic research data for understanding the seismogenic process and mechanism of this earthquake.
基金sponsored by the Fund of Science for Earthquake Resilience(XH21035Y,XH20057)the Earthquake Tracking Track of CEA(2020010211,2018010204)+1 种基金the Earthquake Science and Technology Development Fund of CEA(2016M02,2017IESLZ07)National Natural Science Foundation of China(51478444,41304048)。
文摘To study the crustal movement in the vicinity of the epicenter before the Zhangye MS5.0 earthquake in 2019, the characteristics of crustal deformation before the earthquake are discussed through the GPS velocity field analysis based on the CMONOC data observed from GPS. The baseline time series between two continuous GPS stations and the strain time series of an area among several stations are analyzed in the epicenter area. The resulting time series of baseline azimuth around the epicenter reflects that the energy of the fault in the northern margin of Qilian Mountain is accumulated continuously before 2017. Besides,the movement trend of azimuth slows down after 2017,indicating the stress accumulation on both sides of the seismogenic fault zone has reached a certain degree. The first shear strain and EWdirection linear strain in the epicentral area of the Zhangye MS5.0 earthquake remain steady after 2017,and the surface strain rate decreases gradually after 2016. It is illustrated that there is an obvious deformation loss at the epicentral region three years before the earthquake,indicating that a certain degree of strain energy is accumulated in this area before the earthquake.
