Analyzing the 2020 Mw 6.4 Puerto Rico Earthquake Sequence Based on the Epidemic-Type Aftershock Sequence Model

On 7 January 2020, an Mw 6.4 earthquake occurred on the southwest coast of Puerto Rico, causing severe infrastructure damage and economic property losses. Accompanied with the mainshock, a large number of aftershocks occurred. For investigating the seismological activities, the earthquake sequence is fitted using the ETAS (epidemic-type aftershock sequence) model, based on a seismic catalog with 360 days in the region. The background intensity and the triggered intensity of the sequence are compared, and the variation trend of the parameters of the seismic catalog under different cut-off times are analyzed. Results show that the seismicity has been significantly enhanced during this event. Within 40 days after the mainshock, the background intensity reached the maximum value of 7.26 events/day, while the value is 0.013 events/day before the mainshock. The sequence may be clustered. Both large-magnitude earthquakes and small-magnitude earthquakes are likely to trigger secondary aftershocks. The spatial attenuation of the triggered intensity gradually becomes faster.