A new framework for teleseismic probes of mid-oceanic transform faults

Abstract:

Oceanic transform faults (OTFs) are amongst the simplest tectonic environments on Earth and, as such, represent one of the most attractive locations to investigate how slip is accommodated within the crust. These faults, however, tend to grow in the deep ocean and far away from where local seismic observations are available. This particularity makes the retrieval of accurate OTF source parameters an immensely complicated task and has hindered our ability to characterize their elastic structure and the seismic behavior on a global scale. Several investigations have showed that the seismic recordings of earthquakes along OTFs contain complex patterns of scattered waves that result from the continuous bounces of the P-wave energy trapped in the water column. More recently, we demonstrated that these scattered waves are modelable and can be used to extract valuable information about the absolute location of an earthquake along the fault. In this study, we extend our analysis of OTF earthquakes and combine the modeling of water phases with classical seismological techniques to develop an adaptable framework that allows us to study the seismic behavior of any isolated marine environment in the world. In particular, we focus on the equatorial East Pacific Rise and use relative surface wave travel-time measurements to relocate moderate-magnitude events with respect to those that have been relocated from the analysis of water phases. We also present results of the first attempts to use these high-resolution earthquake locations to probe the fine-scale structure of the fault from teleseismic observations alone. Improving our ability to illuminate the architecture of OTFs in general will result in a tremendous advancement for our understanding on how these fault systems serve as pathways for the hydration of oceanic plates and how they interact with the underlying mantle.