← Back to Sessions

Cyclic Sealing and Drainage on an Oceanic Transform Fault

Description: 

Oceanic transform faults are commonly regarded as conservative plate boundaries, yet their structural complexity near magmatic systems implies a substantive role for fluids. Here we identify tidally modulated tremor from continuous waveforms recorded by an ocean-bottom seismometer network at the Gofar transform fault on the East Pacific Rise, revealing shallow sealing–drainage cycles. Tremor amplitude correlates with semidiurnal tides during intervals of sparse seismicity and low in situ compressional-to-shear wave velocity ratio (Vp/Vs), but this correlation vanishes following M4.0 earthquake swarms, coincident with elevated Vp/Vs. We propose a valve-like sealing–drainage dynamic to explain these observations: sealing traps volatiles, as expressed by low Vp/Vs, and the resulting low permeability causes external stress perturbations to be converted predominantly into pore-pressure variations, enhancing tidal sensitivity. Rupture opens fractures, producing higher Vp/Vs, increasing permeability, and reducing the amplitude of pore-pressure fluctuations; at the same time, a phase lag develops between the pore-pressure response and the external tidal stressing, which weakens the tide–tremor correlation or causes it to disappear, thereby resetting the system. The cycle repeats through hydrothermal resealing. Our results suggest that transform faults can behave as tidally critical permeable systems in which energy release oscillates between fluid-driven tremor and brittle rupture, paced by magmatic volatile supply and progressive healing.

Session: SSJ-SSOC-SSA Joint Session: From Slow to Fast Earthquakes: Bridging the Spectrum of Fault Slip [Poster]

Type: Poster

Date: 4/16/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Hao Yang

Student Presenter: Yes

Invited Presentation: 

Poster Number: 153

Authors