Axial Seamount is a submarine volcano on the Juan de Fuca Ridge with enhanced magma supply from the Cobb Hotspot. Here we compare several deformation model configurations to explore how the spatial component of Axial’s deformation time series relates to magma reservoir geometry imaged by multi-channel seismic (MCS) surveys. To constrain the models, we use vertical displacements from pressure sensors at seafloor benchmarks and repeat autonomous underwater vehicle (AUV) bathymetric surveys covering 2016-2020. We show that implementing the MCS-derived 3D main magma reservoir (MMR) geometry with uniform pressure in a finite element model poorly fits the geodetic data. To test the hypothesis that there is compartmentalization within the MMR that results in heterogeneous pressure distribution, we compare analytical models using various horizontal sill configurations constrained by the MMR geometry. Using distributed pressure sources significantly improved the Root Mean Square Error (RMSE) between the inflation data and the models by an order of magnitude. The RMSE between the AUV data and the models was not improved as much, likely due to the relatively larger uncertainty of the AUV data. The models estimate the volume change for the 2016-2020 inter-eruptive inflation period to be between 0.054-0.060 km3 and suggest that the MMR is compartmentalized, with most magma accumulating in sill-like bodies embedded in crystal mush along the western-central edge of the MMR. The results reveal the complexity of Axial’s plumbing system and demonstrate the utility of integrating geodetic data and seismic imagery to gain deeper insights into magma storage at active volcanoes.

The triggering of large earthquakes on a fault hosting aseismic slip or, conversely, the triggering of slow slip events (SSE) by passing seismic waves involves seismological questions with important hazard implications. Just a few observations plausibly suggest that such interactions actually happen in nature. In this study we show that three recent devastating earthquakes in Mexico are likely related to SSEs, describing a cascade of events interacting with each other on a regional scale via quasi-static and/or dynamic perturbations. Such interaction seems to be conditioned by the transient memory of Earth materials subject to the “traumatic” stressing produced by the seismic waves of the great 2017 (Mw8.2) Tehuantepec earthquake, which strongly disturbed the aseismic slip beating over a 650 km long segment of the subduction plate interface. Our results imply that seismic hazard in large populated areas is a short-term evolving function of seismotectonic processes that are often observable.

Synchronization behavior of large earthquakes (rupture of nearby faults close in time for many cycles) has been reported in many fault systems. The general idea is that the faults in the system have similar repeating interval and are positively coupled through stress interaction. However, many details of such synchronization remain unknown. Here, we built numerical models in the framework of rate/state friction to simulate earthquake cycles on the west Gofar fault, East Pacific Rise. Our model consists of two seismic patches, separated by a barrier patch, constrained by seismic observations. We varied the parameters in the barrier to understand its role on earthquake synchronization. First, we found that static stress transfer can lead to synchronization, opposite to the suggestion by Scholz (2010). Second, the width of the barrier is more important than its strength. When the barrier is narrow enough (no more than half width of the seismic patch in our models), the system can achieve synchronization even with a very strong barrier. Third, for certain simulations, the interaction between the two seismic patches promotes partial rupture in the seismic patches and leads to complex behavior: the system switches from synchronized to unsynchronized over 10-20 cycles. Moreover, the average seismic ratio of the entire fault can be quite low, ranging between 0.2-0.4 because of the barrier patch. We suggest that the existence of large barrier patches contributes significantly to the well-observed low seismic ratio on oceanic transform faults.