Study on the Seismic Activity Patterns Before the Menyuan Ms6.9 and Luding Ms6.8 Earthquakes by Pattern Informatics Method

Abstract

In 2022, four earthquakes with Ms≥6 including the Menyuan Ms6.9 and Luding Ms6.8 earthquakes occurred in the North-South seismic zone, which demonstrated strong seismic activity. Pattern Informatics (PI) method, as an effective medium and long-term earthquake prediction method, has been applied to the prediction of strong earthquakes in mainland China and performed positively. The earthquake catalog with magnitude above Ms3.0 since 1970 provided by China Earthquake Networks Center was taken used in this paper and the ROC method was applied to test the prediction efficiency of the PI method in each region of the North-South seismic zone systematically. Based on this, we selected the area with best ROC result and analyzed the evolution process of the PI hotspot map reflecting the small seismic activity pattern prior to the Menyuan Ms6.9 and Luding Ms6.8 earthquakes. A "forward" forecast for the area was carried out to assess seismic risk. The study shows that: 1) PI behaves better with higher prediction efficiency in areas with smaller differences of seismic activity intensity compared to those with larger differences of seismic activity intensity. 2) In areas with smaller differences of seismic activity intensity, the activity pattern of small earthquakes prior to the Menyuan Ms6.9 and Luding Ms6.8 earthquakes can be obtained by analyzing the spatio-temporal evolution process of the PI hotspot map. 3) The southern Tazang fault in the study area has a PI hotspot evolution process similar to that prior to the strong earthquakes, which suggests the possible seismic hazard in the future. The study could provide some ideas to the seismic hazard assessment and the changing pattern of seismic activity by analyzing the spatial and temporal patterns of seismic activity in areas with high seismicity, such as Southern California, Japan, and the North-South Seismic Zone in China, using the PI method.

Keywords: Luding Ms6.8 earthquake, Menyuan Ms6.9 earthquake, Pattern Informatics method, North-South seismic zone, ROC test, Seismic activity pattern