Synthesizing ocean bottom pressure records including seismic wave and tsunami contributions: Toward realistic tests of monitoring systems

Abstract

AbstractThe present study proposes a method for synthesizing the ocean bottom pressure records during a tsunamigenic earthquake. First, a linear seismic wave simulation is conducted with a kinematic earthquake fault model as a source. Then, a nonlinear tsunami simulation is conducted using the sea bottom movement calculated in the seismic wave simulation. By using these simulation results, this method can provide realistic ocean bottom pressure change data, including both seismic and tsunami contributions. A simple theoretical consideration indicates that the dynamic pressure change caused by the sea bottom acceleration can contribute significantly until the duration of ~90 s for a depth of 4000 m in the ocean. The performance of a tsunami monitoring system was investigated using the synthesized ocean bottom pressure records. It indicates that the system based on the hydrostatic approximation could not measure the actual tsunami height when the time does not elapse enough. The dynamic pressure change and the permanent sea bottom deformation inside the source region break the condition of a simple hydrostatic approximation. A tsunami source estimation method of tFISH is also examined. Even though the synthesized records contain a large dynamic pressure change, which is not considered in the algorithm, tFISH showed a satisfactory performance 5 min after the earthquake occurrence. The pressure records synthesized in this study, including both seismic wave and tsunami contributions, are more practical for evaluating the performance of our monitoring ability, whereas most tsunami monitoring tests neglect the seismic wave contribution.