Overview

Earthquakes and earthquake-induced hazards, such as tsunamis, leave a devastating trail of both humanitarian and economical damages. The overarching theme of my research group will be to understand the important physical mechanisms that govern the occurence of those events within the Earth's crust by developing frameworks for high-throughput computations, theoretical models, experimentation, and eventually integrating machine learning.

FEBE

During my PhD I developed a hybrid approach that couples Finite Element Method with Boundary Element Method, hence the name FEBE, to study long term evolution of fault zones. The implementation is aimed at improving the computational efficiency of large scale earthquake models that are usually intractible while accounting for high resolution fault zone physics such as material heterogenity, inelastic response, and fluid diffusion.

FEBE model illustration
Figure 1: Illustration of the FEBE (Finite Element-Boundary Element) hybrid model for earthquake simulation.

High Resolution Fault Zone Physics

Through the development of FEBE we were able to model the evolution of fault zone with high resolution physics based on observations. This includes modeling fault zones with pre-existing, such as low velocity fault zones, and evolving damage, such as plasticity. By incorporating these physical mechanism we are able to better understand the interactions, or what we call coevolution, between surrounding fault zone and principal slip surfaces.

In addition to developing fault zone structure, fault zones are commonly saturated with fluids. Currently in collaboration with Prof. Lapusta at Caltech, I am working on extending FEBE to incorporate fluid diffusion effects on sequence of earthquakes and aseismic slip.

Supershear Ruptures

As indicated by recent observations earthquakes propagates along frictional interfaces at varying speeds. This can be due to different stressing conditions, or geometrical variations. From a seismic hazard prespective the generated ground excitation is highly dependent on the propagation speed, an effect known as directivity. There are two main domains of speeds at which ruptures can propagate. (A) Subshear where the rupture propagation speed is below the shear wave speed. Typically, below Rayleigh wave speed. (B) Supershear where the rupture propagation exceeds the shear wave speed of the surrounding bulk. Since shear wave propagation within the bulk is by definition limited by shear wave speed, when a rupture exceed shear wave speed the directivity effect is inherently different than a subshear rupture.

My work targets expanding upon our earlier understanding of ground motion characteristics of supershear ruptures to more complex tectonic setting accounting for material heterogenity and complex fault structures.

A second focus of my work on sueprshear earthquakes is to understand natural observations through the lens of this mechanicstic understanding. How can we distinguish between supershear and subshear ruptures from near-fault ground motion records? Is there clear signatures, do these signatures vary in the presence of material heterogenity?.

Tsunamigensis

Combining the computational models of dynamic rupture with nonlinear shallow water wave equation, we were able to understand the mechanisms by which a strike slip earthquake can induce a tsunami despite the limited vertical displacement.