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

Saito, Tatsuhiko; Tsushima, Hiroaki

doi:10.1002/2016jb013195

Cited by 43 publications

(53 citation statements)

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“…For large subduction zone earthquakes that rupture mostly offshore and pose tsunami risk, such near-field measurements remain a challenge. It reinforces the need for real-time offshore seismic and geodetic instrumentation such as ocean bottom strong-motion seismometers, absolute pressure gauges, and GPS-acoustic positioning to improve earthquake and tsunami early warning (e.g., Imano et al, 2015;Saito & Tsushima, 2016;Takahashi et al, 2015;Yokota et al, 2016;Yoshioka & Matsuoka, 2013). Figure 7.…”

Section: 1029/2018jb015962mentioning

confidence: 65%

Geodetic Observations of Weak Determinism in Rupture Evolution of Large Earthquakes

et al. 2018

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The moment evolution of large earthquakes is a subject of fundamental interest to both basic and applied seismology. Specifically, an open problem is when in the rupture process a large earthquake exhibits features dissimilar from those of a lesser magnitude event. The answer to this question is of importance for rapid, reliable estimation of earthquake magnitude, a major priority of earthquake and tsunami early warning systems. Much effort has been made to test whether earthquakes are deterministic, meaning that observations in the first few seconds of rupture can be used to predict the final rupture extent. However, results have been inconclusive, especially for large earthquakes greater than M w7. Traditional seismic methods struggle to rapidly distinguish the size of large‐magnitude events, in particular near the source, even after rupture completion, making them insufficient to resolve the question of predictive rupture behavior. Displacements derived from Global Navigation Satellite System data can accurately estimate magnitude in real time, even for the largest earthquakes. We employ a combination of seismic and geodetic (Global Navigation Satellite System) data to investigate early rupture metrics, to determine whether observational data support deterministic rupture behavior. We find that while the earliest metrics (~5 s of data) are not enough to infer final earthquake magnitude, accurate estimates are possible within the first tens of seconds, prior to rupture completion, suggesting a weak determinism. We discuss the implications for earthquake source physics and rupture evolution and address recommendations for earthquake and tsunami early warning.

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Section: 1029/2018jb015962mentioning

confidence: 65%

Geodetic Observations of Weak Determinism in Rupture Evolution of Large Earthquakes

et al. 2018

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“…When the frequency of the seafloor motion is sufficiently low compared to the fundamental acoustic resonant frequency f 0 ( f < f 0 ), the seafloor pressure change can be approximated as

p = ρ_{0} h_{0} a_{z},

and when the frequency is high ( f > f 0 ) as

p = ρ_{0} c_{0} v_{z},

where ρ 0 is seawater density and a z and v z are the vertical acceleration and velocity of the seafloor motion (hereafter, pressure‐acceleration relationship and pressure‐velocity relationship), respectively (e.g., Bolshakova et al, ; Matsumoto et al, ). Numerical simulation is useful for investigating these relationships (e.g., Kozdon & Dunham, ; Maeda et al, ; Saito, ; Saito & Tsushima, ). Saito and Tsushima () tried to reproduce the dynamic pressure change associated with the 2011 Tohoku‐Oki earthquake by numerical simulation, assuming a uniform slip fault model.…”

Section: Introductionmentioning

confidence: 99%

“…where ρ 0 is seawater density and a z and v z are the vertical acceleration and velocity of the seafloor motion (hereafter, pressure-acceleration relationship and pressure-velocity relationship), respectively (e.g., Bolshakova et al, 2011;Matsumoto et al, 2012). Numerical simulation is useful for investigating these relationships (e.g., Kozdon & Dunham, 2014;Maeda et al, 2013;Saito, 2017;Saito & Tsushima, 2016). Saito and Tsushima (2016) tried to reproduce the dynamic pressure change associated with the 2011 Tohoku-Oki earthquake by numerical simulation, assuming a uniform slip fault model.…”

Section: Introductionmentioning

confidence: 99%

“…Numerical simulation is useful for investigating these relationships (e.g., Kozdon & Dunham, 2014;Maeda et al, 2013;Saito, 2017;Saito & Tsushima, 2016). Saito and Tsushima (2016) tried to reproduce the dynamic pressure change associated with the 2011 Tohoku-Oki earthquake by numerical simulation, assuming a uniform slip fault model. The simple model roughly reproduced the dynamic pressure changes, but not completely.…”

Section: Introductionmentioning

confidence: 99%

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Estimation of Seismic Centroid Moment Tensor Using Ocean Bottom Pressure Gauges as Seismometers

Kubota

Saito

Suzuki

et al. 2017

Geophysical Research Letters

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We examined the dynamic pressure change at the seafloor to estimate the centroid moment tensor solutions of the largest and second largest foreshocks (M w 7.2 and 6.5) of the 2011 Tohoku-Oki earthquake. Combination of onshore broadband seismograms and high-frequency (~20-200 s) seafloor pressure records provided the resolution of the horizontal locations of the centroids, consistent with the results of tsunami inversion using the long-period (≳10 min) seafloor pressure records although the depth was not constrained well, whereas the source locations were poorly constrained by the onshore seismic data alone. Also, the waveforms synthesized from the estimated CMT solution demonstrated the validity of the theoretical relationship between pressure change and vertical acceleration at the seafloor. The results of this study suggest that offshore pressure records can be utilized as offshore seismograms, which would be greatly useful for revealing the source process of offshore earthquakes. Near-field pressure records obtained~20 km from two local earthquakes (M w 7.2 and M w 6.5, National Research Institute for Earth Science and Disaster Resilience (NIED), 2011a, 2011b) (the station and earthquake locations are in Figure 1) are shown in Figure 2. By applying a low-pass filter (>400 s) to the original records (gray), we obtained clear tsunami signals (blue). The maximum tsunami height was~10 cm (Figure 2b) and 1 cm (Figure 2e) for the M w 7.2 and 6.5 earthquakes, respectively. Some studies have estimated earthquake fault models by analyzing such tsunami signals in the OBPGs (e.g.,

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“…Vertical coseismic offsets have been measured accurately offshore using existing seafloor pressure sensors (Bürgmann & Chadwell, 2014;Saito & Tsushima, 2016). Vertical coseismic offsets have been measured accurately offshore using existing seafloor pressure sensors (Bürgmann & Chadwell, 2014;Saito & Tsushima, 2016).…”

Section: Station Configurations and Offshore Data Types Testedmentioning

confidence: 99%

Augmenting Onshore GNSS Displacements With Offshore Observations to Improve Slip Characterization for Cascadia Subduction Zone Earthquakes

Saunders

Haase

2018

Geophysical Research Letters

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For the Cascadia subduction zone, Mw~8 megathrust earthquake hazard is of particular interest because uncertainties in the predicted tsunami size affect evacuation alerts. To reduce these uncertainties, we examine how augmenting the current Global Navigation Satellite Systems (GNSS) network in Cascadia with offshore stations improves static slip inversions for Mw~8 megathrust earthquakes at different rupture depths. We test two offshore coseismic data types: vertical‐only bottom pressure sensors and pressure sensors combined with GNSS‐Acoustic aided horizontal positions. We find that amphibious networks best constrain slip for a shallow earthquake compared to onshore‐only networks when offshore stations are located above the rupture. However, inversions using vertical‐only offshore data underestimate shallow slip and tsunami impact. Including offshore horizontal observations improves slip estimates, particularly maximum slip. This suggests that while real‐time GNSS‐Acoustic sensors may have a long development timeline, they will have more impact for static inversion‐based tsunami early warning systems than bottom pressure sensors.

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

Cited by 43 publications

References 44 publications

Geodetic Observations of Weak Determinism in Rupture Evolution of Large Earthquakes

Geodetic Observations of Weak Determinism in Rupture Evolution of Large Earthquakes

Estimation of Seismic Centroid Moment Tensor Using Ocean Bottom Pressure Gauges as Seismometers

Augmenting Onshore GNSS Displacements With Offshore Observations to Improve Slip Characterization for Cascadia Subduction Zone Earthquakes

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