University of Cambridge > Talks.cam > Bullard Laboratories Wednesday Seminars > Axial Seamount as a unique laboratory to study how stress changes affect earthquake occurrence

Axial Seamount as a unique laboratory to study how stress changes affect earthquake occurrence

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Studying how stress changes modulate earthquake occurrence can shed light on the earthquake nucleation process, as well as the frictional property and stress state of natural faults. In this talk, I will present results from a seafloor observatory that was established on Axial Volcano in 2015. We have set up a monitoring system that computes high-precision earthquake locations in near-real-time. During the first year of operation, ~100,000 earthquakes were located that delineated an outward-dipping ring fault system in a 25 km³ block of crust. Since the fault system experiences periodic tidal loading, this represents a natural laboratory for us to study how earthquakes respond to stress perturbations. We find that the underlying magma chamber inflates and deflates in response to tidal loading, triggering normal faulting earthquakes during low tides and inhibiting them during high tides. The stress dependence of seismicity rate conforms to triggering theory over the whole tidal stress range. There is no triggering stress threshold and stress shadowing is simply a continuous function of stress decrease. The rate-state friction parameter A is an order of magnitude smaller than laboratory measurements. We further find that the earthquake b value is inversely correlated with tidal stress, confirming the stress dependence of earthquake size distribution.

This talk is part of the Bullard Laboratories Wednesday Seminars series.

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