Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the foc...Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored.展开更多
1 SURVEY OF GLOBE SEISMICITY IN 2010 A total of 28 strong earthquakes with Ms ≥ 7.0 occurred in 2010 throughout the world according to the China Seismic Network (Table 1).The strongest was the Chile earthquake measur...1 SURVEY OF GLOBE SEISMICITY IN 2010 A total of 28 strong earthquakes with Ms ≥ 7.0 occurred in 2010 throughout the world according to the China Seismic Network (Table 1).The strongest was the Chile earthquake measuring Ms8.8 on February 27, 2010 (Fig.1).There was an apparent increase in frequency and the energy release of earthquakes in 2010, compared with seismicity in 2009.展开更多
There are controversies on ground motion attenuation relations at the epicentral distance of about 100km. Some models predict that the seismic energy remains almost constant or becomes even stronger with increasing di...There are controversies on ground motion attenuation relations at the epicentral distance of about 100km. Some models predict that the seismic energy remains almost constant or becomes even stronger with increasing distance at this distance, while other models hold that it decreases with increased distance. The divergence lies mainly in whether SmS is stronger than direct S and surface waves at this distance. With the MsS. 9 earthquake sequence in the Yingjiang region of Yunnan Province as an example, we demonstrate that SmS is always 2 - 5 times stronger than direct S waves around the epicentral distance of 100km （which is the post-critical distance for S in this region）. Study of synthetic seismograms suggest that crustal structure has an important effect on the amplitude of post-critical SmS, with simple crust producing strong SmS. This preliminary study confirms that in China, SmS also plays an important role on ground motion at distances around 100km, which demands more studies of post-critical SmS.展开更多
Usually, only crystalline basement is strong enough to store the massive strain energy that can be released in a damaging earthquake. By contrast, sedimentary cover is weak, because of its relatively high porosity and...Usually, only crystalline basement is strong enough to store the massive strain energy that can be released in a damaging earthquake. By contrast, sedimentary cover is weak, because of its relatively high porosity and fluids. Therefore, it generally cannot accumulate enough energy for strong earthquakes. On January 31, 2010, a M5.0 earthquake occurred near the border of Suining and Tongnan in China. It excited strong short-period Rayleigh waves Rg, indicative of its shallow focal depth. The focal depth is constrained to less than 4 km, most probably in the range of 1-3 km, by modeling amplitude dependence on the frequency and waveforms of teleseismic depth phases (pP, sP). Because the local Mesozoic sedimentary cover is about 6 km thick, this earthquake should have occurred in the sedimentary cover. Though some shallow earthquakes with magnitudes up to M4 occur in Paleozoic sediments, this earthquake is the first M5 event studied in Mesozoic sedimentary cover. This event provides a rare opportunity to study seismogenic processes of damaging earthquakes in sedimentary basins.展开更多
In this study, we demonstrate an approach for inverting earthquake source parameters based on high-rate global positioning system （GPS） velocity seismograms. The velocity records obtained from single-station GPS vel...In this study, we demonstrate an approach for inverting earthquake source parameters based on high-rate global positioning system （GPS） velocity seismograms. The velocity records obtained from single-station GPS velocity solutions with broadcast ephemeris are used directly for earthquake source parameter inversion using the Cut and Paste method, without requiring conversion of the velocity records into displacement records. Taking the E1 Mayor-Cucapah earthquake as an example, GPS velocity records from 10 stations with reasonable azimuthal coverage provide earthquake source parameters very close to those from the Global centroid moment tensor （Global CMT） solution. In sparse network tests, robust source parameters with acceptable bias can be achieved with as few as three stations. When the number of stations is reduced to two, the bias in rake angle becomes appreciable, but the magnitude and strike estimations are still robust. The results of this study demonstrate that rapid and reliable estimation of earthquake source parameters can be obtained from GPS velocity data. These parameters could be used for early earthquake warning and shake map construction, because such GPS velocity records can be obtained in real time.展开更多
Earthquake magnitude and rupture duration are among the most important parameters characterizing an earthquake for the purpose of early tsunami warning. While they can be routinely determined from broadband P waveform...Earthquake magnitude and rupture duration are among the most important parameters characterizing an earthquake for the purpose of early tsunami warning. While they can be routinely determined from broadband P waveforms with iterative inver- sion procedures, the inversion procedures may fail when the rupture either lasts longer than the interval between P and later ar- rivals or requires too much time or human intervention. Little contaminated by later arrivals, high frequency P waves are useful for modeling earthquake source processes, though the envelope waveform is affected by strong scattering in lithosphere. With high frequency envelopes from aftershocks as Empirical Green＇s Function （EGF）, the coda effects can be removed and more accurate relative source time function （RSTF） of the main shock can be obtained. Assuming that RSTFs cannot be negative, we use the projected Landweber deconvolution method （PLD） to obtain high frequency RSTFs because PLD method has the ad- vantage of non-negativity, causality, and compactness （finite duration）. We are able to determine rupture durations of four large earthquakes： the 2004 Sumatra-Andaman earthquake, the 2005 Nias event, the 2006 Java event, and the 2011 Tokuko earthquake. The rupture durations of the Sumatra-Andaman, Nias, and Tohuko events are found to be around 550, 1 i0, and 120 s respectively, consistent with previous studies. The rupture duration of the Java event is about 130 s, supporting that the Java event is a tsunami earthquake. The magnitudes of these earthquakes are found to depend on both the amplitude and the duration of the deconvolved waveforms, and can be approximated by integrating these waveforms.展开更多
Previous studies show that mature faults are filled with fault gouge in the shallow part and thus cannot accumulate enough strain energy for earthquakes. Therefore most earthquakes are deeper than 5 km, except those e...Previous studies show that mature faults are filled with fault gouge in the shallow part and thus cannot accumulate enough strain energy for earthquakes. Therefore most earthquakes are deeper than 5 km, except those events occurring on new faults or in intact rocks. From field observation, Wenchuan earthquake is found to rupture the free surface about 200 km, but the rupture may extend underground much further from teleseismic body waves inversion and aftershocks distribution. In the northeastern end of the rupture zone, deep rupture may induce stress increase near the free surface, and trigger shallow earthquakes. An Ms 5.7 aftershock occurred at Qingchuan, northeast end of Wenchuan earthquake fault on July 24, 2008, featuring thrust mechanism with a 3 km source centroid depth. The shallow focal depth is confirmed with the sPL phase recorded at station L0205. As Rayleigh wave is well only developed for source depth less than 1/5 of epicentral distance, the observed large amplitude of Rg at a distance of 15 km implied depth of 3 km or less. Dozens of aftershocks' sPL waveforms are also analyzed to confirm the source depths less than 3 km. On the other hand, no surface ruptures are found by geological survey or InSAR studies. It is strongly suggested that these aftershock sequences initiate fresh rupture in intact rocks triggered by stress increase from the deep co-seismic rupture of the Wenchuan mainshock.展开更多
An M6.5 earthquake occurred on August 3rd, 2014 in Ludian of Yunnan Province in China, causing severe casualty and economic loss. Local broadband waveform inversion with the CAP method demonstrates that the earthquake...An M6.5 earthquake occurred on August 3rd, 2014 in Ludian of Yunnan Province in China, causing severe casualty and economic loss. Local broadband waveform inversion with the CAP method demonstrates that the earthquake is a strike-slip event, with the strike along 70° and 160° for the two nodal planes respectively. However, the geological structure in the epicentral region is complicated with abundant active faults, and it is challenging to identify the seismogenic fault with the focal plane solutions due to nodal-plane ambiguity. We resolved the rupture directivity by measuring the difference between centroid location and hypocenter of the Ludian earthquake with the time shift from CAP inversion, and found that the nodal plane with the strike of 160° is the ruptured fault plane. Moreover, the rupture is found to propagate from northwest to southeast.展开更多
用为 8 h 的测量 GPS 的 coseismic 和 seismic 以后排水量跟随 M w 2011 年 3 月 11 日， coseismic 和 seismic 以后差错的 9.0 仙台地震滑动模型基于一个分层的外壳的模型被开发。主要吃惊的测地学的时刻大小是被测量近似 M w 8.98。...用为 8 h 的测量 GPS 的 coseismic 和 seismic 以后排水量跟随 M w 2011 年 3 月 11 日， coseismic 和 seismic 以后差错的 9.0 仙台地震滑动模型基于一个分层的外壳的模型被开发。主要吃惊的测地学的时刻大小是被测量近似 M w 8.98。slip 展出清楚的反向的特征，与大约 23.3 m 的 hypocenter，和大小附近的最大值。某罢工滑倒行为可以发生在山峰破裂地区的二个方面上。主要吃惊释放的几乎 90% 地震时刻发生在深度不到 40 km。精力由差错释放了在跟随主要吃惊的 8 h 滑倒近似等于 M w 的地震 8.13。与 1.5 m 的最大值， seismic 以后滑倒在 coseismic 破裂差错的西南的部分被集中，它与 M w 的地点和行为同意很好 7.9 余震。这暗示在在主要吃惊以后的 8 h 的 seismic 以后变丑被 M w 主要导致 7.9 余震。另外， seismic 以后 0.20.4 m 滑倒在 coseismic 破裂的下面剧降延期被观察，它可能被在滑倒以后的效果在这个时期期间引起了。展开更多
基金This research was supported by the Joint Earthquake Science Foundation (A07124)the project of"Application of Digital Seismic Data to Short-impending Tracing"of China Earthquake Administration (120602-06-114)
文摘Based on relocating the Jiujiang-Ruichang earthquake sequence which occurred on November 26, 2005 in Jiangxi Province with the double-difference （DD） algorithm and master event technique, the paper discusses the focal mechanism of the main shock （MsS.7） and the probable seismo-tectonics. The precise relocation results indicate that the average horizontal error is 0.31kin in a EW direction and 0.40kin in a NS direction, and the average depth error is 0.48kin. The focal depths vary from 8kin to 14kin, with the predominant distribution at 10kin - 12kin. The epicenter of the main shock is relocated to be 29.69^oN, 115.74^oE and the focal depth is about 10.Skin. Combining the predominant distribution of the earthquake sequence, the focal mechanism of the main shock and the tectonic conditions of N-E- and NW-strike faults growth in the seismic region, we infer that the main shock of the earthquake sequence was caused by a NW striking buried fault in the Rnichang basin. The nature of seismic faults needs to be further explored.
文摘1 SURVEY OF GLOBE SEISMICITY IN 2010 A total of 28 strong earthquakes with Ms ≥ 7.0 occurred in 2010 throughout the world according to the China Seismic Network (Table 1).The strongest was the Chile earthquake measuring Ms8.8 on February 27, 2010 (Fig.1).There was an apparent increase in frequency and the energy release of earthquakes in 2010, compared with seismicity in 2009.
基金sponsored by the Basic Scientific Research Specific Program (02092410),Institute of Earthquake Science,China Earthquake Administration
文摘There are controversies on ground motion attenuation relations at the epicentral distance of about 100km. Some models predict that the seismic energy remains almost constant or becomes even stronger with increasing distance at this distance, while other models hold that it decreases with increased distance. The divergence lies mainly in whether SmS is stronger than direct S and surface waves at this distance. With the MsS. 9 earthquake sequence in the Yingjiang region of Yunnan Province as an example, we demonstrate that SmS is always 2 - 5 times stronger than direct S waves around the epicentral distance of 100km （which is the post-critical distance for S in this region）. Study of synthetic seismograms suggest that crustal structure has an important effect on the amplitude of post-critical SmS, with simple crust producing strong SmS. This preliminary study confirms that in China, SmS also plays an important role on ground motion at distances around 100km, which demands more studies of post-critical SmS.
基金supported by the special fund of the Institute of Earthquake Sciences (02092410)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-116)
文摘Usually, only crystalline basement is strong enough to store the massive strain energy that can be released in a damaging earthquake. By contrast, sedimentary cover is weak, because of its relatively high porosity and fluids. Therefore, it generally cannot accumulate enough energy for strong earthquakes. On January 31, 2010, a M5.0 earthquake occurred near the border of Suining and Tongnan in China. It excited strong short-period Rayleigh waves Rg, indicative of its shallow focal depth. The focal depth is constrained to less than 4 km, most probably in the range of 1-3 km, by modeling amplitude dependence on the frequency and waveforms of teleseismic depth phases (pP, sP). Because the local Mesozoic sedimentary cover is about 6 km thick, this earthquake should have occurred in the sedimentary cover. Though some shallow earthquakes with magnitudes up to M4 occur in Paleozoic sediments, this earthquake is the first M5 event studied in Mesozoic sedimentary cover. This event provides a rare opportunity to study seismogenic processes of damaging earthquakes in sedimentary basins.
基金supported by the National Natural Science Foundation of China(Grant No.41304040)the National Basic Research Program of China(Grant No.2014CB845906-1)the China Postdoctoral Science Foundation(Grant No.2013M541832)
文摘In this study, we demonstrate an approach for inverting earthquake source parameters based on high-rate global positioning system （GPS） velocity seismograms. The velocity records obtained from single-station GPS velocity solutions with broadcast ephemeris are used directly for earthquake source parameter inversion using the Cut and Paste method, without requiring conversion of the velocity records into displacement records. Taking the E1 Mayor-Cucapah earthquake as an example, GPS velocity records from 10 stations with reasonable azimuthal coverage provide earthquake source parameters very close to those from the Global centroid moment tensor （Global CMT） solution. In sparse network tests, robust source parameters with acceptable bias can be achieved with as few as three stations. When the number of stations is reduced to two, the bias in rake angle becomes appreciable, but the magnitude and strike estimations are still robust. The results of this study demonstrate that rapid and reliable estimation of earthquake source parameters can be obtained from GPS velocity data. These parameters could be used for early earthquake warning and shake map construction, because such GPS velocity records can be obtained in real time.
基金supported by Chinese Academy of Sciences (Grant No. KZCX2-YE-142)National Natural Science Foundation of China(Grant Nos. 40974034, 41174086, 41021003)Chinese Academy of Sciences (Grant No. KZCX2-YW-116)
文摘Earthquake magnitude and rupture duration are among the most important parameters characterizing an earthquake for the purpose of early tsunami warning. While they can be routinely determined from broadband P waveforms with iterative inver- sion procedures, the inversion procedures may fail when the rupture either lasts longer than the interval between P and later ar- rivals or requires too much time or human intervention. Little contaminated by later arrivals, high frequency P waves are useful for modeling earthquake source processes, though the envelope waveform is affected by strong scattering in lithosphere. With high frequency envelopes from aftershocks as Empirical Green＇s Function （EGF）, the coda effects can be removed and more accurate relative source time function （RSTF） of the main shock can be obtained. Assuming that RSTFs cannot be negative, we use the projected Landweber deconvolution method （PLD） to obtain high frequency RSTFs because PLD method has the ad- vantage of non-negativity, causality, and compactness （finite duration）. We are able to determine rupture durations of four large earthquakes： the 2004 Sumatra-Andaman earthquake, the 2005 Nias event, the 2006 Java event, and the 2011 Tokuko earthquake. The rupture durations of the Sumatra-Andaman, Nias, and Tohuko events are found to be around 550, 1 i0, and 120 s respectively, consistent with previous studies. The rupture duration of the Java event is about 130 s, supporting that the Java event is a tsunami earthquake. The magnitudes of these earthquakes are found to depend on both the amplitude and the duration of the deconvolved waveforms, and can be approximated by integrating these waveforms.
基金supported by Institute of Earthquake Science China Earthquake Adminis-trator (Grant No.02092410)Knowledge Innovation Program of the Chi-nese Academy of Sciences (Grant Nos.KZCX2-YW-116-1, KZCX2-YW-142)+1 种基金National Natural Science Foundation of China (Grant Nos.40674027,40604004)Earthquake Hazard Reduction Program (Grant No.200808078)
文摘Previous studies show that mature faults are filled with fault gouge in the shallow part and thus cannot accumulate enough strain energy for earthquakes. Therefore most earthquakes are deeper than 5 km, except those events occurring on new faults or in intact rocks. From field observation, Wenchuan earthquake is found to rupture the free surface about 200 km, but the rupture may extend underground much further from teleseismic body waves inversion and aftershocks distribution. In the northeastern end of the rupture zone, deep rupture may induce stress increase near the free surface, and trigger shallow earthquakes. An Ms 5.7 aftershock occurred at Qingchuan, northeast end of Wenchuan earthquake fault on July 24, 2008, featuring thrust mechanism with a 3 km source centroid depth. The shallow focal depth is confirmed with the sPL phase recorded at station L0205. As Rayleigh wave is well only developed for source depth less than 1/5 of epicentral distance, the observed large amplitude of Rg at a distance of 15 km implied depth of 3 km or less. Dozens of aftershocks' sPL waveforms are also analyzed to confirm the source depths less than 3 km. On the other hand, no surface ruptures are found by geological survey or InSAR studies. It is strongly suggested that these aftershock sequences initiate fresh rupture in intact rocks triggered by stress increase from the deep co-seismic rupture of the Wenchuan mainshock.
基金supported by the National Natural Science Foundation of China(Grant No.41274069)National Basic Research Program of China(Grant No.2014CB845901)
文摘An M6.5 earthquake occurred on August 3rd, 2014 in Ludian of Yunnan Province in China, causing severe casualty and economic loss. Local broadband waveform inversion with the CAP method demonstrates that the earthquake is a strike-slip event, with the strike along 70° and 160° for the two nodal planes respectively. However, the geological structure in the epicentral region is complicated with abundant active faults, and it is challenging to identify the seismogenic fault with the focal plane solutions due to nodal-plane ambiguity. We resolved the rupture directivity by measuring the difference between centroid location and hypocenter of the Ludian earthquake with the time shift from CAP inversion, and found that the nodal plane with the strike of 160° is the ruptured fault plane. Moreover, the rupture is found to propagate from northwest to southeast.
基金supported by the Knowledge Innovation Key Program of the Chinese Academy of Sciences (KZCX2-SW-142)the National Natural Science Foundation of China (41021003, 40974034 and 90814009)the Key Project of Earthquake Science (201008007)
文摘用为 8 h 的测量 GPS 的 coseismic 和 seismic 以后排水量跟随 M w 2011 年 3 月 11 日， coseismic 和 seismic 以后差错的 9.0 仙台地震滑动模型基于一个分层的外壳的模型被开发。主要吃惊的测地学的时刻大小是被测量近似 M w 8.98。slip 展出清楚的反向的特征，与大约 23.3 m 的 hypocenter，和大小附近的最大值。某罢工滑倒行为可以发生在山峰破裂地区的二个方面上。主要吃惊释放的几乎 90% 地震时刻发生在深度不到 40 km。精力由差错释放了在跟随主要吃惊的 8 h 滑倒近似等于 M w 的地震 8.13。与 1.5 m 的最大值， seismic 以后滑倒在 coseismic 破裂差错的西南的部分被集中，它与 M w 的地点和行为同意很好 7.9 余震。这暗示在在主要吃惊以后的 8 h 的 seismic 以后变丑被 M w 主要导致 7.9 余震。另外， seismic 以后 0.20.4 m 滑倒在 coseismic 破裂的下面剧降延期被观察，它可能被在滑倒以后的效果在这个时期期间引起了。
