← Back to Sessions

The 2024 Mw7.5 Noto Peninsula Earthquake and Recent Earthquake Swarms in Japan Triggered by the Upward Migration of Deep Crustal Fluids

Description: 

Crustal fluids are considered a significant factor in upper plate earthquakes in subduction zones such as Japan. This hypothesis is supported by geophysical imaging techniques, including seismic velocity and electrical conductivity, revealing fluid-indicative anomalous regions beneath many intraplate earthquakes in Japan. These regions often extend from the subducting slab and are interpreted as concentrated regions of slab-derived fluids. Volcanic activity patterns and isotope ratios further support this interpretation. However, direct evidence linking deep crustal fluids to earthquake generation has remained indirect.

Following the 2011 M9 Tohoku earthquake, evidence of crustal fluid influence on earthquake generation increased significantly. The event reduced accumulated strain, yet earthquake swarms activated after a delay of several weeks, particularly near volcanic regions. These swarms migrated from deep to shallow depths along multiple fault planes. Beneath the source regions, low-velocity zones continuous with the slab and prominent reflectors were observed. These findings suggest that fluid migration within the upper plate was triggered, with ascending fluids subsequently activating earthquake swarms.

The foreshock activity before the 2024 Mw7.5 Noto Peninsula Earthquake showed striking similarities to these swarms, with seismic migration along multiple fault planes suggesting fluid-driven triggering from deeper to shallower depths. In the Noto Peninsula, active faults responsible for past tectonic uplift are widely distributed. The preceding swarm occurred on smaller-scale faults, distinct from the recognized active faults. Upward fluid migration, along with fluid-induced seismic and aseismic slip, likely triggered large fault slip, ultimately causing the 2024 event. Such processes may have contributed to the progressive maturation of active faults and the uplift of the peninsula over time. This case clearly demonstrates that when fluids intrude into a fault nearing failure, large slip events like the Mw7.5 Noto Peninsula Earthquake can be triggered.

Session: Advanced Geophysical Observations, Analytical Methods, and New Insights for Earthquake Swarms - I

Type: Oral

Date: 4/15/2025

Presentation Time: 02:00 PM (local time)

Presenting Author: Keisuke

Student Presenter: No

Invited Presentation: Yes

Poster Number:

Authors