Impact of the M6.4 7 January 2020 Earthquake to Communities and Population of Southwestern Puerto Rico

Session: Early Results from the 2020 M6.4 Indios, Puerto Rico Earthquake Sequence
Type: Oral
Date: 4/30/2020
Time: 01:45 PM
Room: 115
Description: 

Puerto Rico and the Virgin Islands exist within the complex plate boundary between the North American and Caribbean Plates. Consequently, the region has an abundance of seismic activity, which is monitored by the PR (Puerto Rico Seismic Network and the Puerto Rico Strong Motion Program) network. Many of these events have no impact and are not felt by the population whereas others can have devastating impacts. For example: the 6.0Mw September 23, 2019 earthquake in the Mona Canyon, while felt across Puerto Rico, had no concrete impact on the island and its infrastructure due to its distance from the island. In contrast the Southwestern Puerto Rico Earthquake Sequence that initiated on December 28, 2019 and its major 6.4Mw main shock resulted in significant impacts in the region and directly jarred the island’s critical infrastructure. USGS PAGER estimates for the 6.4 Mw event economic losses are on the order of 0-2% of Puerto Rico’s Gross Domestic Product (USGS, 2020). Moreover, the population’s last exposure to a devastating event was 101 years ago, which has been forgotten in the collective memory. In this presentation, the impact of the Southwestern Puerto Rico Seismic Sequence on local communities and infrastructure will be presented. Infrastructure impacts across the region were severe including essentially a complete loss of public buildings and resources in the municipalities of Guánica, Yauco and Gauyanilla. Additionally, thousands of people in the region were displaced from their homes due to damage or fear. Observed infrastructure damage may be related to relatively high PGAs recorded in the region possible due to amplification and/or basin effects. PGA values greater than 0.3g were recorded in the municipalities of Yauco and Utuado. The former is located close to the epicenter where significant PGAs would be expected whereas the latter is located in a prominent topographic bowl floored by alluvial sediment in the interior of the island, relatively removed from the epicenter, indicating a strong geological influence on the shaking intensity and subsequent damage.

Presenting Author: Elizabeth A. Vanacore

Authors