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WITHDRAWN Dynamic Triggering of Earthquakes in Costa Rica

Description: 

WITHDRAWN We document for the first time in the modern seismological era, the dynamic triggering of microseismicity in Costa Rica due to the occurrence of large events at teleseismic distances. Dynamically-triggered failure is typically observed in volcanic or geothermal settings, characterized by the presence of fluid flow and/or high pore pressures weakening fault settings by reducing the normal effective stress, and has been found to be less common in continental or local faults. We use OVSICORI’s broadband seismic stations in Costa Rica to look for teleseismic events with dynamic stresses higher than 1.1 kPa from 2010 until February 2023. We recovered a total of 25 events, including the 6 February 2023 M 7.8 Turkey earthquake. This addition was driven by our observation of increasing seismicity rates along the southern Pacific coast of Costa Rica following this large event. From our observations, two events were identified as prime examples of instantaneous triggering during the arrival of surface waves: the 7.55 Mw Swan Islands earthquake in 2018 and the 7.8 Mw Turkey earthquake in 2023. Both events have a distinctive strike-slip focal mechanism, this is an interesting point considering that the inverse mechanism is predominant and characterizes most of the earthquakes in our catalog. Our results reveal that the triggered seismicity primarily happened in the northern volcanic areas of Costa Rica. However, we also observed significant triggering along the subduction zone in the southern Pacific coast, specifically in Punta Uvita Puntarenas, and, in crustal shallow faults in central Costa Rica, a shear zone with a high population density. Our preliminary results provide evidence that dynamically-triggered earthquakes highlight the presence of weakened faults in central and southern Costa Rica, increasing the possibility of activating cascades of earthquakes that could potentially lead to a large-scale event, like the one devastating the city of Cartago in 1910 or the Osa Peninsula megathrust in 1983.

Session: New Directions in Environmental, Seismic Hazard and Mineral Resource Exploration Studies [Poster]

Type: Poster

Date: 4/17/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Sonia

Student Presenter: Yes

Invited Presentation: 

Poster Number: 111

Authors