Modeling of a short-term slow slip event source incorporating tensile dislocation

Deep low-frequency tremors and short-term slow slip events (S-SSEs) occur closely in space and time, and their sources are located in the transition zone between the locked seismogenic zone and the deeper stable sliding zone. These events are considered to be part of the interseismic process of megathrust earthquakes; however, their deformation mechanism is poorly understood. Geological studies have reported the possibility that both microscopic frictional sliding and tensile fracturing could occur at the source. The cumulative deformation at the source can be detected from geodetic data. Macroscopic slip dislocation, corresponding to cumulative frictional sliding, has been included as a parameter in S-SSE fault modeling; thus, the macroscopic tensile dislocation, corresponding to the cumulative tensile fracturing, can also be estimated. In this study, we re-estimated the S-SSE source model by adding tensile dislocation to the conventional S-SSE fault model. The optimum source model incorporates both tensile and slip dislocations, and is evaluated better than the conventional model that includes only slip dislocation. S-SSE source models are sometimes used to estimate the interseismic slip deficit at the plate boundary; therefore, our re-modeling of the S-SSE source could affect the estimation of anticipated megathrust earthquake sources.