Rupture process and strong ground motion generation of the November 13, 2017 Mw 6.5 Costa Rica earthquake

Abstract

The 13 November 2017 Mw 6.5 Costa Rica earthquake provides an important case study for investigating the relationship between subducted seafloor relief and earthquake source complexity. A first-order finite-fault inversion was conducted using teleseismic broadband and regional strong-motion records processed with the Wavelet Inversion for SliP package (WISP) to resolve low-frequency rupture characteristics. High-frequency source properties were subsequently investigated using the empirical Green’s function (EGF) method. The preferred finite-fault model reveals a fault plane approximately 32 km long and 28 km wide, characterized by a single principal slip patch centered near the hypocenter with a maximum displacement of 1.17 m. High-frequency modeling identifies a compact Strong Motion Generation Area (SMGA) of approximately 62.4 km² located within the northwestern portion of the rupture plane near Jacó city, with an elevated localized stress drop of 32.4 MPa. Synthetic waveforms successfully reproduce observed arrival times, shaking durations, velocity and displacement pulses, and spectral characteristics recorded across the regional accelerographic network, particularly at near-field stations. Ultimately, the compact rupture footprint and high stress drop link the event to a structural asperity from seamount subduction, demonstrating severe near-field shaking risks for Costa Rica’s central Pacific region.