Amir Sagy

Fellowship 2015

ARCHIVE

Amir Sagy is a researcher in the geological survey of Israel and his researches focus on earthquake and fracture mechanics. He completed his M.Sc thesis and PhD work in the Hebrew University of Jerusalem. In his PhD he studied dynamic fracture and combine field work in fault zones and meteorite craters with laboratory experiments which measured fracture velocity in rocks. His post-doc was in UCLA and in UCSC. There, he studied the geometrical evolution of faults and operate field and laboratory optical measurement tools. Currently, he leads the research group of active faulting in the geological survey of Israel. The primary aim of this compilation is for use in seismic-hazard evaluations. His recent researches combine field work in the Dead Sea transform fault area, geological and structural mapping, laboratory experiments and mechanical analysis. He supervised few graduate students and presently he works with two PhD. students and one M.Sc student.

Modelling mechanical evolution of slip surfaces during shear in faults

Since natural faults are rough at all scales, understanding how the non-planarity of the fault affects rupture behavior has become essential for many aspects of seismic hazards and earthquake modeling. Yet, there is a dearth in physical theory for describing or quantifying the evolution of fault surface geometry during slip. The goal of this project is therefore to analyze the geometrical evolution of slip surface and to develop a mechanical model and framework for further research. Our analysis is based on two separated sets of data that we collected recently. First, fault surface geometry has been measured using ground based LiDAR in several field outcrops. Second, we developed unique laboratory method to measure the geometrical evolution of slip surfaces as function of slip distance and normal stress. Our measurements already established that fault surfaces are smoothed by successive slip events. It is however not trivial to connect the experimental results to natural faulting, primarily because the scales of geometrical irregularities and slip magnitudes are diverse in the two systems. In the absence of mechanical model, it is also unknown how wear affects fault geometry on different scales and to what degree rock is ground down under the high normal stresses typical to seismogenic zones.  Our aim is therefore to develop a simple model that quantifies the geometric evolution of fault surface due to the wear of its asperities.