In situ stress state and seismic hazard in the Dayi seismic gap of the Longmenshan thrust belt.

In the Longmenshan thrust belt, the Dayi seismic gap, an area with few earthquakes, is located between the ruptures of the 2008 Wenchuan Earthquake and the 2013 Lushan Earthquake, with a length of approximately 40–60 km. To date, however, the extent of the seismic hazard of the Dayi seismic gap and whether this gap is under high stress are still hotly debated. To further evaluate the seismic hazard of the Dayi seismic gap with regard to stress, two boreholes (1,000 and 500 m deep) were arranged to carry out hydraulic fracturing in situ stress measurement on either side of the Shuangshi-Dachuan fault zone. This zone has a high seismic hazard and the capacity to undergo surface rupture Through the analogy of this new data with stability analysis using Byerlee's Law and existing stress measurement data collected before strong earthquakes, the results show that the area surrounding the Shuangshi-Dachuan fault zone in the Dayi seismic gap (Dachuan Town) is in a state of high in situ stress, and has the conditions necessary for friction slip, with the potential hazard of moderate to strong earthquakes. Our results are the first to reveal the in situ stress profile at a depth of 1,000 m in the Dayi seismic gap, and provide new data for comprehensive evaluation of the seismic hazard in this seismic gap, which is of great significance to explore the mechanism of earthquake occurrence and to help mitigate future disaster. [ABSTRACT FROM AUTHOR]