Shallow Tremors Near the Nankai Trough Activated After the M 7.6 Noto Peninsula Earthquake

Abstract Off the Cape Muroto near the Nankai Trough, small shallow tremor activity was observed by distributed acoustic sensing (DAS) and offshore seismic network DONET after the 2024 M7.6 Noto Peninsula earthquake approximately 600 km away. After the mainshock, DAS continued observation including tremors more stably than DONET; therefore, DAS can be an effective means in monitoring seismicity when a large earthquake occurs. We located these tremors on the western edge of the slow earthquake area by envelope correlation and amplitude attenuation property with distance. These tremors activated several hours after the passage of surface waves of the earthquake. The number of tremors was larger than background tremor activity rate; therefore, this tremor activity can be related to the Noto Peninsula earthquake. A transient loading by the Noto Peninsula earthquake may have advanced the tremor occurrence, or pore pressure redistribution by a stress change may have caused the tremors.