Earthquakes & Geophysics
We are a growing program focused on all aspects of the earthquake problem. We study the physics of shallow and deep earthquakes, the earthquake cycle, the mechanics of faulting, structures and processes in the deep Earth, the geological record of earthquakes, and the ground deformation associated with faulting.
Our specific areas of expertise and interest include: modeling dynamic earthquake ruptures and tsunami; studying continental deformation through space geodesy; simulating fault system behavior; neotectonics and geomorphology; earthquake source seismology; investigating Earth structure and composition; and investigating the mechanics of earthquakes experimentally.
Earthquake rupture, slip and tsunami modeling
We are interested in understanding the physics of the earthquake process. Active research questions include: “Why do some earthquakes become large, while others remain small?” “What geometrical and structural features control the propagation of earthquake rupture and slip?” “What aspects of the seismic source control the generation of strong ground motion?” We also investigate the connection between faulting, seafloor deformation, and the generation and propagation of tsunamis. Our primary tools are numerical/computer models of the dynamic rupture process, including the use of supercomputers and advanced visualization techniques.
Space geodesy and continental deformation
Space geodesy is the study of the shape and movement of the Earth’s surface using satellite data. By using techniques such as InSAR and GPS to measure these movements and therefore the deformation of the Earth's surface, we aim to learn more about processes that occur in the crust. These include earthquakes, the bending of the crust and loading of faults by plate tectonics, slow movements of faults ('fault creep'), and human activities such as geothermal power production.
Fault system simulation
In order to better understand the behavior of large and geometrically complex fault systems, such as the plate boundary fault system in California, we have developed an 'earthquake simulator' – a computer model that can simulate hundreds of thousands of years of fault interactions, using realistic, quasi-dynamic physics. This leverages our previous work on the rate- and state-dependent representation of fault constitutive properties, modeling of seismicity, aftershocks and earthquake triggering, and inverse models that use earthquake rates to map stress changes in space and time. We are currently working on extending these models to study induced seismicity – i.e. earthquakes that are influenced by human activity.
Neotectonics and geomorphology
Southern California is a natural laboratory for studying interactions between faulting behavior and the landscape. Using a variety of techniques, including geological fieldwork, lidar, structure from motion, and terrain analysis, we aim to better understand the long-term geological hazards associated with earthquakes and other related phenomena (such as landslides and debris flows). We also gain insights into these phenomena through comparisons with similar plate boundary systems, such as the Alpine Fault in New Zealand.
Faculty involved: Barth
Earthquake source seismology
Our goal is to understand the physics of earthquakes and fault slip, using seismology as a tool. We investigate a wide spectrum of fault slip behavior including slow earthquakes, tremor, low frequency earthquakes etc. In addition, we image rupture propagation of large, damaging earthquakes to investigate their source properties, slip dynamics and associated hazards. Novel seismic array techniques are developed and cutting edge existing techniques are improved to advance our understanding of earthquakes, faults and related structures.
Faculty involved: Ghosh
Earth structure and composition
We are interested in the structure and composition of Earth, including the crust, and the upper and lower mantle. Faculty combine geochemical analytical facilities, land and oceanographic fieldwork with geophysical computing facilities and seismic experiments to probe Earth's interior, characterizing mantle structures and their influence on surface features, volcanism, geodynamics and tectonic evolution.
Experimental investigation of earthquake mechanics
A particular focus of this group has been the physics of deep earthquakes and the anticrack mechanism that enables them, with subsequent extension to investigation of dehydration embrittlement of serpentinized peridotite and its applications to intermediate-depth earthquakes. More recently, the combination of the high-pressure faulting mechanism and the results of high-speed friction experiments have led to the hypothesis that all earthquakes, including shallow ones, are lubricated by sliding on nanocrystalline products of phase transformation. We are currently testing that hypothesis.