Ultrabroadband Seismic and Tsunami Wave Observation of High‐Sampling Ocean‐Bottom Pressure Gauge Covering Periods From Seconds to Hours

Earth and Space Science

T. Saito¹  T. Kubota¹  W. Suzuki¹  N. Y. Chikasada¹ 

[1] National Research Institute for Earth Science and Disaster Resilience Tsukuba Japan;

关键词: tsunami;    seismic wave;    ocean‐bottom pressure gauge;    seismometer;    tide gauge;    tiltmeter;   

DOI  :  10.1029/2020EA001197

来源: DOAJ

【 摘 要 】

Abstract Recent developments of ocean‐bottom pressure gauges (PG) have enabled us to observe various waves including seismic and tsunami waves covering periods of T ∼ 100–103 s. To investigate the quality for broadband observation, this study examined the broadband PG records (sampling rate of 1 Hz) around Japan associated with the 2010 Chile earthquake. We identified three distinct wave trains, attributed to seismic body waves, Rayleigh waves, and tsunamis. Clear dispersive features in the Rayleigh waves and tsunamis were explained by theories of elastic waves and gravity waves. Quantitative comparison between pressure change and nearby seismograms demonstrated the validity of the theoretical relation between pressure p and vertical acceleration az for ∼3 hr from the origin time. We also found a relationship between p and vertical velocity vz holds only at the first P wave arrival, but not for later arrivals. Similar results were confirmed for various earthquakes with different source‐station distances and magnitudes, suggesting the robustness of these relations. The results demonstrate that the high‐sampling rate (≥1 Hz) is necessary to observe seismic‐wave dispersion and PG can record both seismic waves and tsunamis with reasonable quality for waveform analyses, whereas conventional onshore and offshore seismometers or tide gauges can observe either of seismic waves and tsunamis. Utilizing the high‐sampling PG in combination with the seismic and tsunami propagation theory for estimating earthquake source process or analyzing wave propagation processes in the ocean will deepen our geophysical understanding of the solid‐fluid coupled system in the Earth and contribute toward disaster mitigation.

【 授权许可】

Unknown