On January 1, 2024 at 16:10:09 JST, an M_(j) 7.6 earthquake struck the Noto Peninsula in the southern part of the Sea of Japan. This location has been experiencing an earthquake swarm for more than three years. Here, ...On January 1, 2024 at 16:10:09 JST, an M_(j) 7.6 earthquake struck the Noto Peninsula in the southern part of the Sea of Japan. This location has been experiencing an earthquake swarm for more than three years. Here, we provide an overview of this earthquake, focusing on the slip distribution of the mainshock and its relationship with the preceding swarm. We also reexamined the source areas of other large earthquakes that occurred around the Sea of Japan in the past and compared them with the Matsushiro earthquake swarm in central Japan from1964 to 1968. The difference between the Matsushiro earthquake swarm and the Noto earthquake swarm is the surrounding stress field. The Matsushiro earthquake swarm was a strike-slip stress field, so the cracks in the crust were oriented vertically. This allowed fluids seeped from the depths to rise and flow out to the surface. On the other hand, the Noto area was a reverse fault stress field. Therefore, the cracks in the earth's crust were oriented horizontally. Fluids flowing underground in deep areas could not rise and spread over a wide area in the horizontal plane. This may have caused a large amount of fluid to accumulate underground, triggering a large earthquake. Although our proposed mechanism does not take into account other complex geological conditions into consideration, it may provide a simple way to explain why the Noto swarm is followed by a large earthquake while other swarms are not.展开更多
Since the beginning of the 21st century,major earthquakes have frequently occurred worldwide.To explore the impact of astronomical factors on earthquakes,in this study,the statistical analysis method of correlation is...Since the beginning of the 21st century,major earthquakes have frequently occurred worldwide.To explore the impact of astronomical factors on earthquakes,in this study,the statistical analysis method of correlation is used to systematically analyze the effects of astronomical factors,such as solar activity,Earth’s rotation,lunar declination angle,celestial tidal force,and other phenomena on M≥8 global earthquakes at the beginning of the 21st century.With regard to solar activity,this study focuses on the analysis of the 11-year and century cycles of solar activity.The causal relationship of the Earth’s rotation is not obvious in this work and previous works;in contrast,the valley period of the solar activity century cycle may be an important astronomical factor leading to the frequent occurrence of global earthquakes at the beginning of the 21st century.This topic warrants further study.展开更多
To reveal the seismogenic mechanism of the Luding earthquake, we employed the 118 China Seismic Network stations to collect the P-wave polarity data from each station, which was then used in the P-wave first motion ap...To reveal the seismogenic mechanism of the Luding earthquake, we employed the 118 China Seismic Network stations to collect the P-wave polarity data from each station, which was then used in the P-wave first motion approach to calculate the focal mechanism solution of the M6.8 Luding earthquake that occurred on September 5,2022. We have also studied the loading effect of tectonic stress on the Luding earthquake fault based on the stress field data for the research area. The results indicate that this earthquake was a strike-slip type, the nodal plane I:strike 167°, dip angle 78°, slip angle 2°;Nodal plane II: strike 77°, dip angle 88°, slip angle 168°. The two fault planes’ instability coefficients of the Luding earthquake are examined considering the region’s background stress field’s condition. The nodal plane I in the Moho circle is discovered to practically coincide with the Coulomb failure line and the tangent point of the Moho circle, indicating that this nodal plane has a high instability coefficient compared to the nodal plane II. The conclusion is that the nodal plane I has a higher likelihood of being the seismogenic fault plane, which is congruent with the seismogenic fault plane suggested by the aftershock distribution, the earthquake radiation energy distribution of a single station, and seismic intensity distribution.The Luding earthquake’s focal mechanism is highly like the theoretical focal mechanism of the fault situated at the location where the Coulomb failure line intersects the Mohr circle, demonstrating that background stress is what caused the earthquake. The substantial fault instability and similarity between the solved and theoretical focal mechanisms make it easier to comprehend the loading effect of tectonic stress on the Luding earthquake fault.展开更多
Based on the analysis of coseismic deformation in the macroscopic epicentral region extracted by Differential Interferometric Synthetic Aperture Radar (D-InSAR), and combined with the seismic activity, focal mechanism...Based on the analysis of coseismic deformation in the macroscopic epicentral region extracted by Differential Interferometric Synthetic Aperture Radar (D-InSAR), and combined with the seismic activity, focal mechanism solutions of the earthquake and field investigation, the characteristic of coseismic deformation of MS=8.1 western Kunlunshan Pass earthquake in 2001 was researched. The study shows that its epicenter lies in the northeast side of Hoh Sai Hu; and the seismogenic fault in the macroscopic epicentral region can be divided into two central deformation fields: the west and east segments with the lengths of 42 km and 48 km, respectively. The whole fault extends about 90 km. From the distribution of interferometry fringes, the characteristic of sinistral strike slip of seismogenic fault can be identified clearly. The deformations on both sides of the fault are different with an obviously higher value on the south side. In the vicinity of macroscopic epicenter, the maximum displacement in look direction is about 288.4 cm and the minimum is 224.0 cm; the maximum sinistral horizontal dislocation of seismogenic fault near the macroscopic epicenter is 738.1 cm and the minimum is 551.8 cm.展开更多
Deterministic, probabilistic and composite-grading methods are used to get the possible locations of strong earth-quakes in the future in Norwest Beijing and its vicinity based on the quantitative data and their accur...Deterministic, probabilistic and composite-grading methods are used to get the possible locations of strong earth-quakes in the future in Norwest Beijing and its vicinity based on the quantitative data and their accuracy about active tectonics in the research area and by ordering, some questions in the results are also discussed. It shows that the most dangerous fault segments for strong earthquakes in the future include: segments B and A of the southern boundary fault of the Yangyuan basin, the southern boundary fault of the Xuanhua basin, the east segment of the southern Huaian fault and the east segment of the northern YanggaoTianzhen fault. The most dangerous area is YangyuanShenjing basin, the second one is TianzhenHuaianXuanhua basin and the third dangerous areas are WanquanZhangjiakou and northeast of Yuxian to southwest of Fanshan.展开更多
基金supported by the National Nature Science Foundation of China (No. 42130312)。
文摘On January 1, 2024 at 16:10:09 JST, an M_(j) 7.6 earthquake struck the Noto Peninsula in the southern part of the Sea of Japan. This location has been experiencing an earthquake swarm for more than three years. Here, we provide an overview of this earthquake, focusing on the slip distribution of the mainshock and its relationship with the preceding swarm. We also reexamined the source areas of other large earthquakes that occurred around the Sea of Japan in the past and compared them with the Matsushiro earthquake swarm in central Japan from1964 to 1968. The difference between the Matsushiro earthquake swarm and the Noto earthquake swarm is the surrounding stress field. The Matsushiro earthquake swarm was a strike-slip stress field, so the cracks in the crust were oriented vertically. This allowed fluids seeped from the depths to rise and flow out to the surface. On the other hand, the Noto area was a reverse fault stress field. Therefore, the cracks in the earth's crust were oriented horizontally. Fluids flowing underground in deep areas could not rise and spread over a wide area in the horizontal plane. This may have caused a large amount of fluid to accumulate underground, triggering a large earthquake. Although our proposed mechanism does not take into account other complex geological conditions into consideration, it may provide a simple way to explain why the Noto swarm is followed by a large earthquake while other swarms are not.
文摘Since the beginning of the 21st century,major earthquakes have frequently occurred worldwide.To explore the impact of astronomical factors on earthquakes,in this study,the statistical analysis method of correlation is used to systematically analyze the effects of astronomical factors,such as solar activity,Earth’s rotation,lunar declination angle,celestial tidal force,and other phenomena on M≥8 global earthquakes at the beginning of the 21st century.With regard to solar activity,this study focuses on the analysis of the 11-year and century cycles of solar activity.The causal relationship of the Earth’s rotation is not obvious in this work and previous works;in contrast,the valley period of the solar activity century cycle may be an important astronomical factor leading to the frequent occurrence of global earthquakes at the beginning of the 21st century.This topic warrants further study.
基金supported by the Special Found of the Institute of Geophysics, China Earthquake Administration (DQJB22B18)
文摘To reveal the seismogenic mechanism of the Luding earthquake, we employed the 118 China Seismic Network stations to collect the P-wave polarity data from each station, which was then used in the P-wave first motion approach to calculate the focal mechanism solution of the M6.8 Luding earthquake that occurred on September 5,2022. We have also studied the loading effect of tectonic stress on the Luding earthquake fault based on the stress field data for the research area. The results indicate that this earthquake was a strike-slip type, the nodal plane I:strike 167°, dip angle 78°, slip angle 2°;Nodal plane II: strike 77°, dip angle 88°, slip angle 168°. The two fault planes’ instability coefficients of the Luding earthquake are examined considering the region’s background stress field’s condition. The nodal plane I in the Moho circle is discovered to practically coincide with the Coulomb failure line and the tangent point of the Moho circle, indicating that this nodal plane has a high instability coefficient compared to the nodal plane II. The conclusion is that the nodal plane I has a higher likelihood of being the seismogenic fault plane, which is congruent with the seismogenic fault plane suggested by the aftershock distribution, the earthquake radiation energy distribution of a single station, and seismic intensity distribution.The Luding earthquake’s focal mechanism is highly like the theoretical focal mechanism of the fault situated at the location where the Coulomb failure line intersects the Mohr circle, demonstrating that background stress is what caused the earthquake. The substantial fault instability and similarity between the solved and theoretical focal mechanisms make it easier to comprehend the loading effect of tectonic stress on the Luding earthquake fault.
文摘Based on the analysis of coseismic deformation in the macroscopic epicentral region extracted by Differential Interferometric Synthetic Aperture Radar (D-InSAR), and combined with the seismic activity, focal mechanism solutions of the earthquake and field investigation, the characteristic of coseismic deformation of MS=8.1 western Kunlunshan Pass earthquake in 2001 was researched. The study shows that its epicenter lies in the northeast side of Hoh Sai Hu; and the seismogenic fault in the macroscopic epicentral region can be divided into two central deformation fields: the west and east segments with the lengths of 42 km and 48 km, respectively. The whole fault extends about 90 km. From the distribution of interferometry fringes, the characteristic of sinistral strike slip of seismogenic fault can be identified clearly. The deformations on both sides of the fault are different with an obviously higher value on the south side. In the vicinity of macroscopic epicenter, the maximum displacement in look direction is about 288.4 cm and the minimum is 224.0 cm; the maximum sinistral horizontal dislocation of seismogenic fault near the macroscopic epicenter is 738.1 cm and the minimum is 551.8 cm.
基金National major basic-theory planning project Mechanism and Prediction of Strong Earthquake (95130105) and the Key Project from China Seismological Bureau (95040803).
文摘Deterministic, probabilistic and composite-grading methods are used to get the possible locations of strong earth-quakes in the future in Norwest Beijing and its vicinity based on the quantitative data and their accuracy about active tectonics in the research area and by ordering, some questions in the results are also discussed. It shows that the most dangerous fault segments for strong earthquakes in the future include: segments B and A of the southern boundary fault of the Yangyuan basin, the southern boundary fault of the Xuanhua basin, the east segment of the southern Huaian fault and the east segment of the northern YanggaoTianzhen fault. The most dangerous area is YangyuanShenjing basin, the second one is TianzhenHuaianXuanhua basin and the third dangerous areas are WanquanZhangjiakou and northeast of Yuxian to southwest of Fanshan.
