PGA and MMI Instrumental Intensity Distribution in the Puerto Rico Island Upon the 2020 Puerto Rico M6.4 Earthquake

Session: Early Results from the 2020 M6.4 Indios, Puerto Rico Earthquake Sequence [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The Puerto Rico region has a significant seismic hazard due to large and moderate local earthquakes. Such relatively infrequent onshore/offshore seismicity, as well as the temporal and spatial patterns is currently not well understood. To correctly quantify this hazard, it is necessary to improve our understanding and knowledge of the: (i) seismicity, (ii) specific fault structures identification and the (iii) seismotectonic understanding of the region. Fault structure dimensions are important because it helps to define fault segmentation, which controls the sizes and expected earthquakes occurrence.

Earthquakes of the of January 2020 sequence, were recorded by the Puerto Rico Strong Motion Program (PRSMP). The largest earthquake, M6.4, occurred on January 7/2020, was located offshore at ~8 km south of Indios Town of Guayanilla Municipality. The closest and largest epicentral distances were 12 km and ~100 km (YAC2 and CR03 stations respectively). Preliminary focal mechanism solution, reported in https://earthquake.usgs.gov/earthquakes/eventpage indicate oblique normal faulting at shallow depth as the result of slip on either a moderately dipping plane striking just north of west, or on a moderately dipping plane striking just west of south. At the location of this event, the North America and the Caribbean plates converges at a rate of ~20 mm/yr towards the west-southwest. The location and focal mechanism solution are consistent with an intraplate tectonic setting within the lithosphere of the Caribbean plate. Preliminary results of Peak Ground Acceleration (PGA) and instrumental intensity (MMI) distribution in the Puerto Rico Island are here presented. The geometric mean of the largest PGA reached ~0.38g at YAC2 and 0.017g at CR03. Local site effects are evident, being ~0.35g at station UTD2 located at ~35 km and 0.005g in SNG2 station located ~36 km. The estimated instrumental intensities varied from VIII, nearby YAC2, to III nearby CYY2 station.

Presenting Author: Carlos I. Huerta-Lopez

Authors