For earthquakes (M≥4.0) occurring along and around the East Anatolian fault zone and the Dead Sea fault zone within ten years immediately before the MW7.8 Gaziantep earthquake,Türkiye,of February 6,2023,we explo...For earthquakes (M≥4.0) occurring along and around the East Anatolian fault zone and the Dead Sea fault zone within ten years immediately before the MW7.8 Gaziantep earthquake,Türkiye,of February 6,2023,we explored the correlation between seismicity and the earth's rotation.We statistically evaluated the correlation using the Schuster's test.The results are quantitatively assessed by a p-value.We found a clear downward trend in the p-values from early 2020 to late 2022 in the studied region.We also obtained a spatial distribution of the p-values showing a low p-value area near the northeastern end of the aftershock zone.Although the stress induced by the rotation of the earth is very weak,it could control the earthquake occurrence when the focal medium is loaded to the critical state to release a large earthquake.The decrease in the b-value in the Gutenberg-Richter (G-R) relation is considered in the form of the tectonic stress increase in the crust.We investigated the b-value as a function of time in the study region.We found that the b-value had decreased for about eleven years before the p-value started to decrease,with a relative reduction of 57%.Therefore,the result of the lower p-values obtained in the present study infers that the earthquakes were dominated by the earth's rotation prior to the MW7.8 Türkiye earthquake due to a critical state of the focal region.展开更多
Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface r...Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.展开更多
In this study,we analyzed 100 three-component strong ground motion records observed within 200 km of the causative fault of the 6 February 2023 M_(W)7.8 Pazarcık(Kahramanmaraş)Earthquake in SE Türkiye.The wavelet...In this study,we analyzed 100 three-component strong ground motion records observed within 200 km of the causative fault of the 6 February 2023 M_(W)7.8 Pazarcık(Kahramanmaraş)Earthquake in SE Türkiye.The wavelet method was utilized to identify and analyze the characteristics of pulse-like ground motions in the near-fault region,while considering the uncertainty of the pulse orientation during the analysis.Our investigation focused on the effects of the focal mechanism and rupture process on the spatial distribution,pulse orientation,and maximum pulse direction of the observed pulse-like ground motion.We also analyzed the amplitude and period of the observed ground pulses and the effect of long-period amplification on the ground motion response spectra.Our results indicated the following:(1)A total of 21 typical ground velocity pulses were observed during this earthquake,exhibiting complex characteristics due to the influence of the strike-slip mechanism and rupture directivity.Most ground pulses(17 out of 21)were recorded within 20 km of the fault,in a wide range of orientations,including normal and parallel to the fault direction.The waveforms exhibited unidirectional features,indicating the effects of left-lateral fault slip.Distinct pulses observed more than 20 km from the fault were mainly oriented normal to the fault.The waveforms were bidirectional with double-or multi-round trips as a result of rupture directivity.(2)The amplitudes of the observed pulses ranged from 30.5 to 220.0 cm/s,with the largest peak velocity of 220.0 cm/s observed at Station 3138.The pulse periods ranged from 2.3 to 14.5 s,with the longest pulse period of 14.5 s observed at Station 3116.The amplitude and period of the pulses observed during this earthquake were comparable to those of similar-magnitude global earthquakes.The amplitude of the pulses decreased significantly with increasing fault distance,whereas the pulse period was not significantly affected by the fault distance.(3)Compared with non-pulse records,the velocity pulse records had a pronounced amplification effect on the acceleration response spectra near the pulse period,with factors ranging from 2.1 to 5.8.The larger velocity pulses also significantly amplified the velocity response spectra,particularly over the long periods.This significant amplification effect of the pulses on the response spectra leads to empirical models underestimating the long-period earthquake ground motion.展开更多
基金supported by the China National Key Research and Development Program(2022YFF0800601)the Special fund of the Institute of Geophysics,China Earthquake Administration (DQJB23Z09)。
文摘For earthquakes (M≥4.0) occurring along and around the East Anatolian fault zone and the Dead Sea fault zone within ten years immediately before the MW7.8 Gaziantep earthquake,Türkiye,of February 6,2023,we explored the correlation between seismicity and the earth's rotation.We statistically evaluated the correlation using the Schuster's test.The results are quantitatively assessed by a p-value.We found a clear downward trend in the p-values from early 2020 to late 2022 in the studied region.We also obtained a spatial distribution of the p-values showing a low p-value area near the northeastern end of the aftershock zone.Although the stress induced by the rotation of the earth is very weak,it could control the earthquake occurrence when the focal medium is loaded to the critical state to release a large earthquake.The decrease in the b-value in the Gutenberg-Richter (G-R) relation is considered in the form of the tectonic stress increase in the crust.We investigated the b-value as a function of time in the study region.We found that the b-value had decreased for about eleven years before the p-value started to decrease,with a relative reduction of 57%.Therefore,the result of the lower p-values obtained in the present study infers that the earthquakes were dominated by the earth's rotation prior to the MW7.8 Türkiye earthquake due to a critical state of the focal region.
基金funded by the Basic Research Program of the Institute of Earthquake Forecasting,China Earthquake Administration(Grant Nos.CEAIEF20220102,2021IEF0505,and CEAIEF2022050502)the National Natural Science Foundation of China(Grant Nos.42072248 and 42041006)the National Key Research and Development Program of China(Grant Nos.2021YFC3000601-3 and 2019YFE0108900)。
文摘Both M_(W) 7.8 and M_(W) 7.5 earthquakes occurred in southeastern Türkiye on February 6,2023,resulting in numerous buildings collapsing and serious casualties.Understanding the distribution of coseismic surface ruptures and secondary disasters surrounding the epicentral area is important for post-earthquake emergency and disaster assessments.High-resolution Maxar and GF-2 satellite data were used after the events to extract the location of the rupture surrounding the first epicentral area.The results show that the length of the interpreted surface rupture zone(part of)is approximately 75 km,with a coseismic sinistral dislocation of 2-3 m near the epicenter;however,this reduced to zero at the tip of the southwest section of the East Anatolia Fault Zone.Moreover,dense soil liquefaction pits were triggered along the rupture trace.These events are in the western region of the Eurasian Seismic Belt and result from the subduction and collision of the Arabian and African Plates toward the Eurasian Plate.The western region of the Chinese mainland and its adjacent areas are in the eastern section of the Eurasian Seismic Belt,where seismic activity is controlled by the collision of the Indian and Eurasian Plates.Both China and Türkiye have independent tectonic histories.
基金supported by the National Key Research and Development Program of China (No. 2022YFC3003503)the Special Fund of the Institute of Geophysics, China Earthquake Administration (No. DQJB20B23)+1 种基金supported by the Istanbul Technical University Research Fund (ITU-BAP)by the the Alexander von Humboldt Foundation Research Fellowship Award through the Humboldt-Stiftung Follow-Up Program
文摘In this study,we analyzed 100 three-component strong ground motion records observed within 200 km of the causative fault of the 6 February 2023 M_(W)7.8 Pazarcık(Kahramanmaraş)Earthquake in SE Türkiye.The wavelet method was utilized to identify and analyze the characteristics of pulse-like ground motions in the near-fault region,while considering the uncertainty of the pulse orientation during the analysis.Our investigation focused on the effects of the focal mechanism and rupture process on the spatial distribution,pulse orientation,and maximum pulse direction of the observed pulse-like ground motion.We also analyzed the amplitude and period of the observed ground pulses and the effect of long-period amplification on the ground motion response spectra.Our results indicated the following:(1)A total of 21 typical ground velocity pulses were observed during this earthquake,exhibiting complex characteristics due to the influence of the strike-slip mechanism and rupture directivity.Most ground pulses(17 out of 21)were recorded within 20 km of the fault,in a wide range of orientations,including normal and parallel to the fault direction.The waveforms exhibited unidirectional features,indicating the effects of left-lateral fault slip.Distinct pulses observed more than 20 km from the fault were mainly oriented normal to the fault.The waveforms were bidirectional with double-or multi-round trips as a result of rupture directivity.(2)The amplitudes of the observed pulses ranged from 30.5 to 220.0 cm/s,with the largest peak velocity of 220.0 cm/s observed at Station 3138.The pulse periods ranged from 2.3 to 14.5 s,with the longest pulse period of 14.5 s observed at Station 3116.The amplitude and period of the pulses observed during this earthquake were comparable to those of similar-magnitude global earthquakes.The amplitude of the pulses decreased significantly with increasing fault distance,whereas the pulse period was not significantly affected by the fault distance.(3)Compared with non-pulse records,the velocity pulse records had a pronounced amplification effect on the acceleration response spectra near the pulse period,with factors ranging from 2.1 to 5.8.The larger velocity pulses also significantly amplified the velocity response spectra,particularly over the long periods.This significant amplification effect of the pulses on the response spectra leads to empirical models underestimating the long-period earthquake ground motion.
