My research is directed towards better understanding of the mechanics and physics of earthquakes through analytical and numerical modeling.  Destructive shallow earthquakes initiate as frictional instabilities on tectonic boundaries and other faults in the Earth’s crust and propagate as dynamic frictional cracks under extreme conditions:  The slipping zone extends with average crack tip speeds of 2-3 km/s, the two sides of the fault slide with particle velocities of about 1 m/s on average, and the normal stresses that press the two sides of the fault together are of the order of 100 MPa.  At the same time, faults are loaded with plate velocities of the order of 10^-9 m/s and exhibit complex patterns of quasi-static (aseismic) slip, with processes of earthquake nucleation, postseismic slip, and aseismic transients.  Detailed understanding of physics and mechanics of faults is critical to our ability to estimate and prevent damage caused by this natural hazard and to answer many existing fundamental questions about earthquakes such as whether they can be predicted.  The fundamental questions that motive my research are: What controls the spatio-temporal distribution of slip on faults?  How do earthquakes nucleate and arrest?  Can we distinguish between the beginning of large and small events?  What causes supershear propagation?  What governs aseismic slip?  How do thermal effects due to shear heating in rapid slips – such as flash heating, pore-fluid pressurization, and melting – influence dynamic rupture propagation and overall fault behavior?  How can we describe these and other fault processes and incorporate them into constitutive laws with numerically tractable parameters? What is the stress state on the faults?  What causes aftershock sequences?  Which aspects of fault physics are relevant to ground motions and estimates of earthquake hazard?  How can we model fault heterogeneities, off-fault damage, fault systems, fault interactions, and tectonic loading in a realistic and manageable way?

For more information, please see my research web site:
http://www.gps.caltech.edu/~lapusta