Update for Puerto Rico - January 12, 2020

Aftershock Forecast

The USGS aftershock forecast, updated on Jan. 12, indicates the likelihood of a M 6.0 or larger aftershock over the next 7 days is 11 percent. There is also a high likelihood of M 3.0+ aftershocks in the coming week; these M 3.0+ quakes may be felt near the epicenters. The rate of aftershocks will continue to decline over time. A large aftershock or new mainshock would, once again, increase the frequency and magnitude of aftershocks. Estimates for other magnitude ranges and time periods can be found in the forecast.

30-Day Aftershock Scenarios

Based on our aftershock forecasts, USGS has modeled three possible scenarios for this earthquake sequence as it evolves over the next month. These scenarios represent what could happen from January 12 to February 12, 2020. Only one of these scenarios will occur. The earthquakes in these scenarios would occur in the areas near where aftershocks are happening now. Regardless of scenario, earthquakes will continue to occur for days, months, or potentially years to come. It is very unlikely the aftershocks will cease completely within the next month.

Scenario One (most likely): 76 percent chance

The most likely scenario is that aftershocks will continue to decrease in frequency over the next 30 days, with no further earthquakes similarly sized to the M 6.4 that occurred on Jan. 7, 2020 (i.e., will be less than M 6.0). Some of these moderately sized aftershocks (M 5.0+) may cause localized damage, particularly in weak structures. Smaller magnitude earthquakes (M 3.0+), when at shallow depth, may be felt by people close to the epicenters.

Scenario Two (less likely): 21 percent chance

A less likely scenario is an earthquake occurring of similar size as the M 6.4 event. This is called a “doublet”: when two large earthquakes of similar size occur closely in time and location. This earthquake could cause additional damage in the same region and increases the number of aftershocks.

Scenario Three (least likely):  3 percent chance

A much less likely scenario than the previous two scenarios is that recent earthquakes could trigger an earthquake significantly larger than the M 6.4 that occurred Jan. 7, 2020 (i.e., M 7.0 and above). While this is a small probability, if such an earthquake were to occur, it would have serious impacts on communities nearby. This sized earthquake would also trigger its own aftershock sequence, so the rate of small and moderate earthquakes would increase again.