Preliminary report of coseismic surface rupture(part)of Türkiye's M_(W)7.8 earthquake by remote sensing interpretation

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.

Pulse-like ground motion observed during the 6 February 2023 M_(W)7.8 Pazarcık Earthquake(Kahramanmaraş,SE Türkiye)

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.

2023年2月6日土耳其M_(W)7.8帕扎尔哲克地震地表破裂特征分析

2023年2月6日土耳其东南部连续发生2次7级以上破坏性地震,造成大量人员伤亡和建筑物损坏。基于高分辨率遥感系统解译了帕扎尔哲克7.8级地震地表破裂空间分布,结合野外科考验证、基于立体像对生成的高分辨率数字地表模型及余震精定位数据,对帕扎尔哲克7.8级地震地表破裂特征进行分析。该次地震地表破裂主要沿先前断层迹线发育,总长度约为320 km。地表破裂位置地貌特征、野外典型位置调查结果及余震精定位结果均显示该次地震以左旋走滑运动为主,局部伴有小规模垂向运动。最大左旋位移位于东安纳托利亚断裂帕扎尔哲克段,蒂尔克奥卢以南地表破裂逐渐不连续,左旋位错不明显。

基于FK方法和GP14.3震源模型的2023年土耳其M_(w)7.8级地震宽频地震动合成

本文合成了2023年2月6日土耳其M_(w)7.8地震的地震动时空场。首先,依据USGS网站提供的V s30数据和全球地壳模型Crust1.0数据,构建了土耳其南部地区的地下一维速度结构模型;其次,依据美国地质调查局(USGS)发布的断层滑动量及破裂前端分布结果,构建了此次地震的GP14.3运动学混合震源模型;然后,采用作者提出的FK方法对本次地震进行了0~10 Hz的宽频三分量地震动合成。通过合成结果与距离震中50 km范围内地震动较强的8个台站强震记录及相应反应谱的比较,检验了方法的可靠性和模型的适用性;最后,重点分析了土耳其东南部的加济安泰普市及附近地区地震动时空场特征。结果表明:1)本文计算的加济安泰普市区范围内的NS向PGA接近180 cm/s^(2)、PGV接近100 cm/s,伊斯拉希耶镇地区的EW向PGA高达560 cm/s^(2)、PGV高达150 cm/s,地震动强度比较大。2)基于本文强地面运动合成结果得到的加济安泰普市区范围内的地震烈度为VII度,伊斯拉希耶镇地区的地震烈度高达IX度,与USGS给出的结果一致。3)此次土耳其M_(w)7.8地震呈现明显的近断层地震动集中性效应、地面永久位移以及破裂方向性效应。

GPS测定的2020年阿拉斯加M_(W)7.8地震震时地表动态变形及永久同震形变场

以UNAVCO公布的阿拉斯加地区GPS 1 Hz和30 s采样观测数据为基础,采用双差定位方法分别对两种采样率的数据进行处理分析,获得2020年7月22日阿拉斯加M_(W)7.8地震震时地表动态变形及同震三维形变场。结果显示,震中270 km范围内高频GPS震时波形明显,最大振幅达600 mm。根据各个GPS站的动态形变波形振幅及响应时间认为,其振幅和响应时间受地震的破裂传播方向和场地效应影响较大。静态同震位移矢量指向震中,同震位移大小基本符合随震中距离增大而减小的特征,除站点AC13外,其中距离震中最近站点的最大水平位移达26.7 cm。GPS测定的同震形变表明,2020年阿拉斯加地震是发生在阿拉斯加阿留申俯冲大断裂的一次逆冲型地震。

2016年新西兰凯库拉M_(W)7.8地震同震破裂及子断层间相互影响

2016年11月13日新西兰南岛东北部凯库拉M_(W)7.8地震同震破裂比较复杂,其发震断层多达12条.通过反演InSAR同震位移,确定了断层同震位错分布.结果表明:最大位移量发生在Kekerenbgu断层北部,约13.5 m,以右旋走滑运动为主,而最大逆冲错动发生在Jor-dan Thrust 断层和 Papatea 断层上,板块界面上的最大滑移位于Jordan Thrust断层下.为进一步分析各子断层破裂间的相互关系,基于各发震断层同震位错反演结果,分别计算了破裂过程中先破裂断层在后续破裂断层上的同震库仑应力变化.结果表明:相邻断层间引起的最大同震库仑应力变化量级在MPa范围,除Hundalee断层和Jordan Thrust东北部断层上的同震库仑应力减少外,其他断层都位于库仑应力增加的区域,增加的量级可达MPa,远高于一般认为的触发阈值0.01 MPa.据此认为,在此次地震复杂的多断层破裂过程中,静态库仑应力是破裂传播和断层触发的关键因素,在很大程度上促进了后续断层的破裂.

2020年阿拉斯加M_(W)7.8地震断层滑动反演及其触发影响研究

2020年7月22日,在北美板块和太平洋板块交界区的阿拉斯加半岛阿留申俯冲带上发生了M_(W)7.8逆冲地震,三个月后距震中西南80 km处发生了M_(W)7.6走滑地震,一年后距震中东南50 km处发生了M_(W)8.2逆冲地震.本文基于GPS同震形变,利用非负最小二乘方法反演了M_(W)7.8地震的断层同震破裂滑动分布,研究其变形特征,并基于地震位错理论计算了该地震对后续两个地震的库仑应力影响.地震断层滑动反演结果显示地震矩为9.28×10^(20) N·m,矩震级为M_(W)7.8;断层破裂滑移自震中沿断层向SWW向延伸,在震中西南侧断层滑动量较大,深度范围集中在25~45 km,最大滑动量为2.26 m.同震形变符合海沟特大地震的逆冲断层弹性回跳理论模式.库仑应力变化计算结果显示2020年阿拉斯加M_(W)7.8地震的库仑应力加载触发了M_(W)7.6走滑地震,并加速了2021年M_(W)8.2逆冲地震的发生.

2016年新西兰凯库拉M_(W)7.8地震前空间大气扰动

采用欧洲中尺度天气预报中心(ECMWF)的ERA5温度数据和GPS观测数据,提取2016-11-13新西兰凯库拉M_(W)7.8地震前的温度异常和电离层VTEC异常,探讨震前空间大气扰动的时空变化特征。结果表明,2016-11-08、09震中以北分别出现温度异常和VTEC异常。温度异常具有增温-增温加强-增温衰减-增温高峰-快速衰减的变化特征,这与岩石形变-破裂释放热的过程基本一致;随着高度上升,增温面积及幅度逐渐减小,符合地震热异常在自下而上的抬升过程中逐渐消退的趋势。