Improvement of near-field tsunami forecasting method using ocean-bottom pressure sensor network (S-net)

Abstract

Since the installation of a dense cabled observation network around the Japan Trench (S-net) by the Japanese government that includes 150 sensors, several tsunami forecasting methods that use the data collected from the ocean floor sensors were developed. One of such methods is the tsunami forecasting method which assimilates the data without any information of earthquakes. The tsunami forecasting method based on the assimilation of the ocean-bottom pressure data near the source area was developed by Tanioka in 2018. However, the method is too simple to be used for an actual station distribution of S-net. To overcome its limitation, we developed an interpolation method to generate the appropriate data at the equally spaced positions for the assimilation from the data observed at sensors in S-net. The method was numerically tested for two large underthrust fault models, a giant earthquake (Mw8.8) and the Nemuro-oki earthquake (Mw8.0) models. Those fault models off Hokkaido in Japan are expected to be ruptured in the future. The weighted interpolation method, in which weights of data are inversely proportional to the square of the distance, showed good results for the tsunami forecast method with the data assimilation. Furthermore, results indicated that the method is applicable to the actual observed data at the S-net stations. The only limitation of the weighted interpolation method is that the computed tsunami wavelengths tend to be longer than the actual tsunamis wavelength.

Improving the Constraint on theMw7.1 2016 Off‐Fukushima Shallow Normal‐Faulting Earthquake With the High Azimuthal Coverage Tsunami Data From the S‐Net Wide and Dense Network: Implication for the Stress Regime in the Tohoku Overriding Plate

“…Recent studies have started to utilize S-net ocean-bottom seismometers to investigate the seismotectonics and geodynamics in the Tohoku subduction zone (Dhakal et al, 2021;Hua et al, 2020;Matsubara et al, 2019;Nishikawa et al, 2019;Sawazaki & Nakamura, 2020;Takagi et al, 2019Takagi et al, , 2020Tanaka et al, 2019;Uchida et al, 2020;Yu & Zhao, 2020). The S-net also incorporates ocean-bottom pressure gauges (OBPGs), which are expected to be utilized for tsunami forecasts (e.g., Aoi et al, 2019;Inoue et al, 2019;Mulia & Satake, 2021;Tanioka, 2020;Tsushima & Yamamoto, 2020;Wang & Satake, 2021;. The other potential contributions to the earth sciences of the S-net OBPG have also been demonstrated, such as understanding the wave propagation process in the ocean as well as the rupture process of subseafloor earthquakes Kubota et al, 2021;Saito et al, 2021).…”

Monitoring the 2021 Mw 8.2 Alaska Earthquake by an Offshore Seismic and Fluid Pressure Observation Network and Implications for Ocean‐Crust Dynamic Coupling

“…Understanding the mechanisms of seafloor pressure variations is important for multiple scientific disciplines. Besides its wide use in studying various types of ocean dynamics such as interannual upwelling variations, seasonal circulation variations, mesoscale oceanic eddies, ocean currents (e.g., Chelton et al, 2007;Hughes et al, 2018;Osborne & Burch, 1980;Saldías et al, 2021;Thomson et al, 2014), and tsunami generation and propagation (e.g., Kubota et al, 2022;Mulia & Satake, 2021;Tanioka, 2020;Thomson et al, 2011), seafloor pressure monitoring has been used as a geodetic tool to monitor crustal deformation associated with submarine earthquakes and slow slip events (Davis et al, 2015;Hino et al, 2014;Ito et al, 2013;Sun et al, 2017;Wallace et al, 2016). For the same purpose, many recent studies were focused on untangling the mixed oceanographic and geophysical signals in ocean bottom pressure records (Dobashi & Inazu, 2021;Fredrickson et al, 2019;Gomberg et al, 2019;He et al, 2020;T.…”

“…larger-scale forearc structure and geodynamic processes (Hua et al, 2020;Uchida et al, 2020;Yu & Zhao, 2020), and enabling real-time earthquake monitoring and tsunami early warning (Aoi et al, 2019;M. Inoue et al, 2019;Mulia & Satake, 2021;Tanioka, 2020;Thomson et al, 2011). To date, studies of offshore earthquake monitoring in real time via cable-connected networks were mostly focused on small earthquakes (up to M w 7.1) (e.g., Kubota, Kubo, et al, 2021;Tréhu et al, 2018;Wallace et al, 2016).…”

Meteotsunami Observed by the Deep‐Ocean Seafloor Pressure Gauge Network Off Northeastern Japan

“…Furthermore, it has been reported that much smaller tsunamis with amplitudes less than one centimeter related to the Mw 6.0 Off‐Iwate earthquake on August 20, 2016, were observed (Kubota, Saito, & Suzuki, 2020; Figure 1c). S‐net is also expected to be utilized for the real‐time tsunami forecasts (e.g., Inoue et al., 2019; Suzuki et al., 2020; Tanioka, 2020; Tsushima & Yamamoto, 2020). In addition to earthquake‐induced tsunamis, or seismic tsunamis, the OBPs can record other oceanographic phenomena, such as infragravity waves and internal tides (e.g., Fukao et al., 2019; Tonegawa et al., 2018).…”