Análise da sequência sísmica de 2017 no Noroeste da Bacia Potiguar

Abstract

The understanding of earthquake occurrence in intraplate areas has been one of the most difficult tasks in Seismology. Attenuation of seismic waves in these areas is lower compared to border plate regions. As a consequence, even moderate magnitude earthquakes can represent great hazard. In this case, assessing the stress field in intraplate regions is important to better understanding the earthquake generating mechanisms. We analyzed 241 earthquakes of the 2017 seismic sequence in NW Potiguar Basin and estimated the stress regime. Seismically defined faults were determined for 4 high-precision relocated NWSE- and NE-SW-trending clusters. Faulting intersection acting in one of this clusters was representative for suggest Intersection model for intraplate earthquakes as possible explanation about why moderate size earthquake occur in the study region. Another cluster presented an en echelon fault with a clear spatiotemporal evolution and occurrence of almost entire activity in very short period, which suggests energy build-up and rapidly release between this fault segment. We were be able to calculate composite focal mechanism for three clusters, with predominant sinistral strike-slip faulting. The inversion of focal mechanisms reinforce evidence for a superposition of local and regional stresses, with major compressional axis subparallel to continental equatorial margin.