Improving the constraint on the Mw 7.1 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

Back‐Projection Imaging of a Tsunami Excitation Area With Ocean‐Bottom Pressure Gauge Array Data

“…S‐net consists of 150 stations as its final form in the present; however, 25 stations located in an outer‐trench region were not installed when this event occurred. Station S2N13, which was located just above the focal area, did not record any pressure changes because the pressure observation component of this station appears not to have worked correctly (Kubota, Kubo, et al., 2021).…”

“…These arrays enable us to observe tsunamis propagating across such an array directly. Tsunami recordings by using an OBPG array have been analyzed by various approaches: for example, to estimate tsunami source processes (e.g., Fukao et al., 2018; Hossen et al., 2015; Kubota, Kubo, et al., 2021), to reconstruct tsunami wavefields by data assimilation (e.g., Gusman et al., 2016; Wang & Satake, 2021), to detect scatterers of tsunami waves by the beamforming method (Kohler et al., 2020), and to derive a phase velocity map of tsunamis by the eikonal tomography (Lin et al., 2015).…”

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

“…We also compare the observed feature of these tsunami‐like waves with those of the seismic tsunamis observed by S‐net. The dominant period of the waves is almost comparable to the tsunamis associated with the Mw 7.0 Off‐Fukushima earthquake (Figure 1d; Kubota, Kubo, et al., 2021; Tsushima & Yamamoto, 2020), although the maximum amplitudes of a few hectopascals are almost five times smaller than those for this earthquake (∼10 hPa = 10 cmH 2 O, supposing that a pressure change of 1 hPa is equivalent to a sea‐height change of 1 cm) and tsunami wave trains propagating to both north and south directions can be recognized. On the other hand, the maximum amplitudes are similar to those for the Mw 6.0 Off‐Iwate earthquake (Figure 1c), although the dominant periods for this earthquake were much shorter (∼300 s, Kubota, Saito, & Suzuki, 2020).…”

“…S‐net has started to be widely utilized for monitoring ocean waves related to earthquakes. One of the largest tsunamis so far recorded by S‐net was that associated with the Mw 7.0 Off‐Fukushima earthquake on November 21, 2016 (Kubota, Kubo, et al., 2021; Tsushima & Yamamoto, 2020; Figure 1d). 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).…”

Earthquake Rupture and Tsunami Generation of the 2015 Mw 5.9 Bonin Event Revealed by In Situ Pressure Gauge Array Observations and Integrated Seismic and Tsunami Wave Simulation

“…Recent developments of offshore seismic and geodetic observations have advanced our understanding of the ocean (e.g., Bürgmann & Chadwell, 2014; Favali et al., 2015). The ocean‐bottom absolute pressure gauge (APG) has also driven fundamental studies of tsunamis (e.g., Fukao et al., 2018; Kubota, Kubo, et al., 2021; Kubota, Saito, Chikasada, & Sandanbata, 2021; Levin & Nosov, 2009; Rabinovich & Eblé, 2015; Saito & Kubota, 2020) and seafloor geodesy (e.g., Wallace et al., 2016). Recent wide and dense offshore observation networks will drive such studies more actively (Aoi et al., 2020; Kaneda et al., 2015; Kawaguchi et al., 2015).…”