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Deep Earthquakes Can Generate Larger and Far-reaching Co-seismic Displacements Than Shallow Events

Description: 

In the past several decades, the utilization of geodetic data has enabled remarkable advances in understanding earthquake physics. So far, such seismic studies have mainly focused on shallow (0-60 km) earthquakes, while surface displacements produced by intermediate (100–300 km) and deep (300+ km) earthquakes remaining underexplored since these displacements have been mostly thought to be small. However, recent studies reporting significant co-seismic displacements produced by deeper events—e.g., >1 cm displacements resulting from the 598.1-km deep 2013 M_W8.3 Okhotsk event—challenge this assumption. Yet, the contribution from deep earthquakes to the Earth’s surface deformation relative to that from shallower earthquakes is still poorly understood.

Therefore, in this study, we conduct a detailed comparative GNSS analysis to bridge this gap. To achieve this goal, we evaluate the observed co-seismic displacements generated by the 598.1-km deep 2013 M_W8.3 Okhotsk event and the 22.4-km deep 2015 M_W8.3 Illapel event, which have nearly identical seismic moment and focal mechanism. Surprisingly, we find that a deep earthquake can generate larger co-seismic displacements than a shallow earthquake within a broad region. Through modeling tests, we demonstrate that the phenomenon is primarily attributed to the geometry of the 3D displacement fields produced by earthquakes, not from the effect of the Earth’s curvature. In addition, we find that the deep earthquake can produce detectable far-field displacements (e.g., larger than 1 mm), sometimes at greater distances than those from the shallow event. For example, GNSS stations in the Hokkaido region (>13° from the earthquake) record clear geodetic signals from the deep Okhotsk earthquake. These results highlight that intermediate and deep earthquakes are important sources of Earth’s surface displacements that should be incorporated in our current geodetic framework; furthermore, co-seismic displacement data may bring new insights into the deep rupture process.

Session: The Landscape Record of Earthquakes and Faulting - III

Type: Oral

Date: 4/16/2026

Presentation Time: 02:45 PM (local time)

Presenting Author: Sifang Chen

Student Presenter: Yes

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