中国地震局地质研究所 Yingfeng Zhang研究组报道了天山西南前陆柯坪褶皱冲断带的应变容纳与地震灾害，来自2022年柯坪6.0级地震的启示。该研究于2023年2月23日发表于国际一流学术期刊《JGR地球》杂志上。

在这项研究中，研究人员利用干涉合成孔径雷达测量，远震体波、近场强震数据(SM)和2022年柯坪6.0级地震的重新定位余震，研究了中国天山西南部柯坪褶皱冲断带(KFTB)的应变积累。研究首次对地震后干涉合成孔径雷达的时间序列进行了近场强震数据建模和分析，研究结果证实了主震和余震的垂直分离，前者位于弱滑脱层上，后者位于基底内的断层上。对干涉合成孔径雷达的时间序列分析表明，地震后变形主要发生在断裂滑脱层正上方的伸展断层上。同震破裂的静态应力传递不能解释这些观测结果。

研究小组推测，流体流动和沿已存在的断平面的高孔隙压力可能降低了断层强度，并参与了该余震群的演化。研究结论是，柯坪褶皱冲断带中的压应变是由薄和厚的断层以及整个地壳厚度的地震活动变形混合调节的。具体地说，该研究团队认为观测到的缩短部分是由弱滑脱层上罕见的大地震所调节的。

据悉，前陆地区的应变积累对认识造山过程和地震灾害具有重要意义。该边界区的物质不均匀，特别是沉积盖层与基底的对比，影响了应变调节和断层行为。这种效应的表现之一是干涉合成孔径雷达(InSAR)推导的滑移模型和相应的余震波束的深度分离，这种垂直分离的假设仍然存在争议。

附：英文原文

Title: Strain accommodation and seismic hazards of the Kalpin fold-and-thrust belt, southwestern Tian Shan foreland, China: Insights from the 2020 Mw 6.0 Kalpin earthquake

Author: Yingfeng Zhang, Xinjian Shan, Wenyu Gong, Guohong Zhang, Chunyan Qu, Tao Li

Issue&Volume: 2023-02-23

Abstract: Strain accumulation in foreland zones is important for understanding mountain-building processes and seismic hazards. Material heterogeneity in this border zone, particularly the contrast between sedimentary cover and basement, affects strain accommodation and fault behavior. One manifestation of this effect is depth separation of Interferometric Synthetic Aperture Radar (InSAR)-derived slip models and corresponding aftershock clusters; hypotheses for this vertical separation remain controversial. In this study, we investigated strain accumulation in the Kalpin fold-and-thrust belt (KFTB) of southwestern Tian Shan, China, using the integration of InSAR measurements, teleseismic body-waves, near-field strong motion data (SM), and relocated aftershocks of the 2020 Mw 6.0 Kalpin earthquake. The SM modeling and analysis of post-seismic InSAR time series are performed first time for this earthquake. Our results confirm a vertical separation of the mainshock and aftershock cluster, with the former on a weak décollement and the latter on faults within the basement. InSAR time series analysis shows that post-seismic deformation was dominated by afterslip on a splay fault directly above the ruptured décollement. Static stress transfer of co-seismic rupture cannot explain these observations. We speculate that fluid flow and high pore pressure along pre-existing fault planes may have reduced the fault strength and been involved in the evolution of this aftershock cluster. We conclude that compressive strain in the KFTB is accommodated by a mixture of thin- and thick-skin faulting and seismicity deformation across the entire crustal thickness. Specifically, we suggest that the observed shortening is partly accommodated by infrequent large earthquakes on the weak décollement.

DOI: 10.1029/2022JB025328

Source: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JB025328