Abstract

Earthquakes with magnitudes M_w = 6.4 and M_w = 7.1 occurred in July 2019, one after the other with an interval of 34 hours, several kilometers apart, near the town of Ridgecrest, Kern County, California, USA. There was a moderate shock with a magnitude of M_w = 5.8 in 1995 in the immediate vicinity of the epicenters of the future earthquakes. A strong earthquake with M_w = 7.4 occurred about a hundred kilometers to the north in 1872. To study the seismic deformation process in connection with these events, data from continuous GPS observations at 51 station were used, with a daily recording interval. The initial observation epoch was 13 years prior to the latest events (July 2006), and the final epoch was about a month (August 2019) after those. The study area has a diameter of about 250 km and includes the epicenters of modern and historical earthquakes. Digital models of the distribution of horizontal, total shear and dilatation deformations were obtained for each day of observations. Incorporation of the time sequence of the obtained models into an accelerated kinematic visualization of the seismic deformation process (https://www.researchgate.net/publication/343577013_Ridgecrest_total_shear_strain_and_seismicity_evolution) revealed some interesting features. The onset of shear deformation extremum was close to the time of the moderate earthquake (M_w = 5.2), which occurred 10 years before the events of 2019, about 70 km from it, and which presumably initiated the trigger mechanism of the future seismic rupture with the beginning of the development of a weakened elongated zone in the area of the Coso volcanic field. The area of anomalous shear spread in the direction of the future events and reached their epicenters at the time of the main shocks. An analysis of the space-time distribution of the length of the surface displacement vectors showed the possibility of determining the location of a future strong event based on long-term continuous GPS observations in seismic areas.

中文翻译：

---

2019 年 7 月美国里奇克莱斯特地震前后 13 年 GPS 观测的地面运动和变形分析

摘要

2019 年 7 月发生了震级M _w = 6.4 和M _w = 7.1 的地震，地震发生在美国加利福尼亚州克恩县 Ridgecrest 镇附近，间隔为 34 小时，相隔几公里。1995 年在未来地震的震中附近发生了M _w = 5.8的中度地震。M _{w 的}强烈地震= 7.4 发生在 1872 年以北约 100 公里处。为了研究与这些事件相关的地震变形过程，使用了 51 个站的连续 GPS 观测数据，每天记录一次。最初的观测纪元是在最近事件（2006 年 7 月）之前 13 年，最后一个纪元是在这些事件之后大约一个月（2019 年 8 月）。研究区直径约 250 公里，包括现代和历史地震的震中。每天的观测都获得了水平、总剪切和膨胀变形分布的数字模型。将获得的模型的时间序列合并到地震变形过程的加速运动学可视化中 (https://www.researchgate. net/publication/343577013_Ridgecrest_total_shear_strain_and_seismicity_evolution）揭示了一些有趣的特征。剪切变形极值的出现与中震发生时间接近（M _w = 5.2)，它发生在 2019 年事件前 10 年，距离它约 70 公里，并且可能引发了未来地震破裂的触发机制，并开始在科索火山场。异常切变区向未来事件的方向扩散，并在主震发生时到达震中。对地表位移矢量长度的时空分布的分析表明，可以根据地震区的长期连续 GPS 观测确定未来强事件的位置。