Afternoon Update for Puerto Rico - January 7, 2020

Release Date:

Earthquake Update and Aftershock Forecast

The USGS National Earthquake Information Center is preparing to deploy six portable seismometers to Puerto Rico to supplement the seismometers already part of the Puerto Rico Seismic Network. These seismometers, which will be used to help better monitor earthquakes in this area, may be operational by the end of this week. Observations from seismic monitoring equipment will improve our ability to characterize and forecast earthquakes which will help protect lives and property. USGS works in partnership with the PRSN and the Puerto Rico Strong Motion Program at University of Puerto Rico Mayaguez to collect seismic data and monitor earthquakes in the region.

"After the devastating Hurricane Maria occurred in Puerto Rico, the federal government invested in rebuilding damaged seismic stations in the region," said USGS Director Jim Reilly. “These stations have made it possible for the USGS and our partners at the Puerto Rico Seismic Network to provide more accurate and rapid information about the earthquakes and their possible impacts along with better forecasts of potentially damaging aftershocks.”

Portable Seismic Station

Two portable sensors: a strong motion sensor (to record strong shaking that can be felt) and a broadband sensor (to record weak motion for detecting small earthquakes) buried into the ground to detect earthquakes. These stations can be quickly deployed and send real-time data back to the USGS via cellular telemetry immediately after they are installed. (Public domain.)

Seismicity and seismic monitoring stations

The map above shows seismicity (orange circles) and seismic monitoring stations (triangles). Seismic stations that have been recently upgraded are emphasized in red. (Public domain.)

Since the M 4.7 event on December 28, 2019, over 500 M 2+ earthquakes have occurred in this region (as of 2PM EST, 01/07/20), 32 of which were M 4+, including the January 6th M 5.8 and the M 6.4 event on January 7th and its aftershocks.

Aftershock Forecast

Earthquake forecasts are created using a statistical analysis based on past earthquakes and are presented in terms of probabilities of earthquakes of a given size occurring. The current forecast, issued at 15:24 eastern on Jan 7, 2020, estimates that over the next 1 Week there is a 7 percent chance of one or more aftershocks that are larger than magnitude 6.4. It is highly likely that there will be many smaller earthquakes (M>3) over the next 1 Week. Magnitude 3 and above events are large enough to be felt near the epicenter. The rate of aftershocks will decline over time, but a large aftershock can increase the numbers again, temporarily. This forecast may change as the earthquake sequence continues to develop.