https://orcid.org/0000-0002-9505-4524
Abstract
This study aims to understand the variation of the correlation fractal dimension and static stress changes associated with the 2019 Puerto Rico sequence with special reference to the January 2020 6.4 mainshock. On examining the seismicity data from 1988 to 2020, we find a shift in the seismicity pattern after the 2019 Puerto Rico sequence. A detailed examination of changes in the correlation fractal dimension () indicates diffused seismicity throughout the study region until the year 2003 that is demonstrated by relatively high values. Toward the end of 2019, a drastic drop in is observed; it is associated with a tight clustering of events to the south‐southwest of Puerto Rico Island (PRI), suggesting the onset of the 2019 sequence. We observed a persistent clustering and significant drop in before the 6.4 earthquake, hinting at the presence of a numerical precursor for this event. Over 30 yr of historical earthquakes have contributed positive Coulomb stress distributions mainly in the northern region of PRI. A deflection in this pattern was reflected after the 2019 Puerto Rico sequence. Based on the static stress analysis, we demonstrated that the 6.4 mainshock was triggered by the 2019 Puerto Rico sequence. The new cluster of events, which contains the 6.4 mainshock, exhibits higher stress levels in the south‐southwest region of PRI. The eastern end of Septentrional fault (SF), the zone between SF and North Puerto Rico Slope fault, the middle segment of South Puerto Rico Slope fault, South Lajas fault, Punta Montalva fault, and Central fault are the highly stressed regions at present. Stress perturbation induced by the destructive 6.4 event on the adjacent fault system is a potential threat for PRI, where population density is very high. The combined analysis of and static stress changes indicates the presence of a numerical precursor and highly stressed regions southwest of PRI.
