One problem is that of opening fractures along glacier beds, specifically as rapidly propagating hydraulic fractures that are driven by turbulent underflow of highly pressurized melt-water.  Such hydraulic fractures can occur from the catastrophic draining, through the glacier, of large summer melt-water lakes at the glacier surface, a process of much interest for rapid deglaciation.  Another cause is sub-glacial flooding (a Jökulhlaup) from a lake impounded by a later undermined ice dam.  The relation between driving pressure at the fracture mouth and rupture speed is determined, albeit approximately, based on work with V. C. Tsai, and compared to observations from rapid draining of a massive supra-glacial lake on the Greenland ice sheet.

The other problem involves earthquakes on maturely slipped crustal faults.  Progress is summarized on using geologic evidence on fault zone core structure (remarkably thin, sub-mm shear zones) and laboratory-supported descriptions of frictional weakening at high slip rates (showing strong reduction of friction, presumably by flash heating) to rationalize the otherwise puzzling lack of pronounced heat outflow and lack of at least shallow frictional melting along major tectonic faults.  It is argued that the flash heating process, together with weakening by thermal pressurization of pore fluid within fault bordering damage zones, are primary weakening mechanisms active from the start of essentially all events.  Spontaneous dynamic rupture modeling, with E. M. Dunham and H. Noda, which embodies those primary mechanisms shows how faults can be statically strong yet dynamically weak, and operate under low overall driving stress, in a manner that generates negligible heat and seems consistent with known seismic constraints on slip, stress drop, and self-healing rupture mode.