← Back to Sessions

The Magnitude Difference Between Mainshocks and Their Largest Aftershock Increases With Depth for Shallow and Intermediate-Depth Earthquakes Within the Japan Subduction Zone

Description: 

Earthquakes at all depth ranges, from the surface to ~700 km depth, are observed to share many similar source properties, but the number and size of aftershocks are observed to be larger for shallow earthquakes than for deeper earthquakes. This change in aftershock behavior may be caused by a change in the rupture mechanism and/or fault properties with increasing pressure and temperatures with increasing depth. The cause of this change can be investigated by studying the change in aftershock behavior with depth and across the transition zone from shallow to intermediate-depth earthquakes. Using the largest aftershock of an aftershock sequence as a proxy for aftershock productivity, we quantify how the magnitude difference (∆M), time delay (∆T), and the distance (∆D) between the mainshock and largest aftershock change with depth within the Japan subduction zone. From January 1983–February 2019, the Japan Meteorological Agency (JMA) hypocenter catalog contains 911 mainshocks (local magnitude M_J ≥ 5.0; 0–200 km depth). While ∆T and ∆D do not change with depth for these mainshocks, average ∆M values show a statistically significant gradual increase with depth from ~1.0 at the surface to ~3.0 at 200 km depth. Increasing ∆M values suggest that, as depth increases, more energy is partitioned to the mainshock relative to the aftershock sequence. This partitioning may be attributed to a less complex fault geometry that promotes a more complete mainshock rupture or decreasing structural heterogeneity resulting in a less localized stress transfer for aftershock triggering.

Session: Structure and Properties of Subducting Slabs and Deep Earthquakes [Poster]

Type: Poster

Date: 4/19/2023

Presentation Time: 08:00 AM (local time)

Presenting Author: Kyle P. Macy

Student Presenter: Yes

Invited Presentation: 

Authors