Analysis on the Characteristic of Sequence and Aftershock Forecasting for Lushan 6.1 Earthquake on Jun. 1, 2022

Shengfeng Zhang, & Yongxian Zhang

Published September 11, 2022, SCEC Contribution #12286, 2022 SCEC Annual Meeting Poster #203

In Jun 1, 2022, a MS6.1 earthquake with focal depth of 17 km occurred in Lushan, Sichuan which place has also occurred the Lushan MS7.0 earthquake in Apri. 20, 2013 and the distance between these two events is 9 km. Through the scientific research focused on this event using many technique means and disciplines, this event has been primarily acknowledged that it occurred on Shuangshi-Dachuan fault. In the scientific research work around this strong event, probability forecasting for the potential of aftershocks using statistical models can not only provide the proof to understanding the what will occur in the next days, but also list the information of the processional research to the public society, which is also an important work to meet the need of popularization of science. The temporal Epidemic Type Aftershock Sequence (ETAS) model is a good tool in statistical seismology and also has a good performance to give a short term forecasting. To analysis the characteristic of the sequence of this earthquake, we used ETAS model to fit the feature of sequence using the 20 days’ events after the mainshock and described the attenuation in time and the ability to trigger next offsprings. At the same time, we conducted a short term forecasting for next 3 days and give the probability and occurrence rate of aftershocks with different target magnitude. The result suggests that the earthquake sequence changes to a stable state from 5th day and after that the attenuation rate and the ability to trigger next offsprings tend to normal level. Statistical method, such as Receiver Operating Characteristic (ROC) method, was used to evaluate the performance of this experiment and it suggests that this forecasting model have a good performance than the random guess, especially for the aftershocks with magnitude above 3.0 and 3.5. Through this practical application, we find that the probabilistic forecasting and performance evaluation work conducted using ETAS model can effectively provide scientific and technological support for the scientific investigation.

Key Words
Lushan 6.1 earthquake，Epidemic-Type Aftershock-Sequences model, Probability forecasting, ROC test

Citation
Zhang, S., & Zhang, Y. (2022, 09). Analysis on the Characteristic of Sequence and Aftershock Forecasting for Lushan 6.1 Earthquake on Jun. 1, 2022. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Forecasting and Predictability (EFP)