AT42-20 Cruise Report for the 2019-2021 Gofar Transform Fault Earthquake Prediction Experiment, Leg 1: OBS Deployment and Rock Dredging

Abstract

The goal of this cruise was to deploy 51 ocean bottom seismometers (OBS) and conduct rock dredges at the Quebrada/Discovery/Gofar (QDG) transform fault systems, with a focus on the Gofar system. QDG is located in the equatorial east Pacific on the East Pacific Rise (Figure 1). Sections of the Gofar and Discovery systems rupture with large (Mw > 5.3) earthquakes every 5-6 years, while only one event of this size has occurred on Quebrada in the last 35 years. Variations in along-strike earthquake behavior during these seismic cycles are further constrained by results from a 2008 OBS experiment on QDG. The 2008 experiment revealed the presence of ‘rupture zones’, which fail quasi-periodically in M6 earthquakes, and ‘rupture barriers’, which repeatedly stop large ruptures, yet undergo intense foreshock sequences. The current OBS deployment on Gofar is thus aimed at recording variations in stress build up, stress release, and fault strength within the context of a well-known seismic cycle.