A physical model for widespread near‐surface and fault zone damage induced by earthquakes

I present a rigorous unifying interpretation of the well‐documented widespread near‐surface and fault zone damage induced by earthquakes by simulating three‐dimensional dynamic rupture propagation on a vertical strike‐slip fault. Stresses in the crust are depth‐dependent and material response is governed by the Drucker‐Prager yield criterion. I show that material yielding induced by seismic waves under the low confining pressure causes widespread near‐surface damage. Because the confining pressure increases with depth, the yielding zone at depth is narrowly confined near the fault, but its thickness broadens dramatically near the surface, forming a “flower‐like” damage zone. The fault zone damage at depth is induced by large dynamic stresses associated with the rupture front, while is induced by strong seismic waves ahead of the rupture front near the Earth's surface. These results have important implications for the formation and evolution of fault zones and possibly for the dynamic triggering of earthquakes as well.