Inhomogeneous precursor characteristics of rock with prefabricated cracks before fracture and its implication for earthquake monitoring

Abstract

Abstract. Earthquake precursor and earthquake monitoring are always important in the earthquake research field, even if there is still debatable about the existence of earthquake precursor. Laboratory rupture experiment is a useful technique to simulate and make an insight into the complex mechanisms of earthquakes. Five marble samples with prefabricated cracks are used for uniaxial loading experiments to investigate whether there is a precursory signal before rock fracture, and to simulate the rupture process of strike-slip fault and its surrounding area. The existence of precursory signal is confirmed by the coefficient of variation (CV) results, from which we can see two patterns which are known as seismicity acceleration and quiescence before an earthquake. Moreover, these CV findings are applied to determine the locations of large deformation sampling points on the rock surface at different loading stages, which indicates that such kinds of points migrate towards the prefabricated cracks as the rock approaches rupture. Similar results are obtained when we consider actual seismicity at the northern end of the San Andreas Fault in California. It provides a crucial evidence to prove the existence and role of precursor characteristics. In this case, three kinds of seismic monitoring models are designed to find out how to arrange the locations of seismic stations in the case of limited number of stations, so as to monitor these precursor characteristics more effectively.