A Local Anomaly of the Stress State of the Earth's Crust before the Strong Earthquake (M = 7.1) of July 5, 2019, in the Area of Ridgecrest (Southern California)

The evolution of the stress–strain state of the Earth's crust in Southern California during the preparation period (from January 1, 2019 until August 15, 2019) of the strong (M = 7.1) earthquake that occurred on July 5, 2019 in the area of the town of Ridgecrest is analyzed using a method based on a constructed geomechanical model and the parameters of current seismicity. An anomaly of the maximum values of the ultimate strength parameter of rocks and the consistent pattern of migration of this anomaly over this period of time are revealed. This pattern is also detected for another earthquake with M = 7.2 that occurred in Southern California on April 4, 2010. The nature of migration of such anomalies and their localization (within a few months) near the epicenters of such seismic events indicate processes of earthquake preparation and can serve as their precursors. This indicates the possibility of using the proposed method for monitoring areas of seismic hazard in order to predict strong earthquakes.