Near-field tsunami forecast system based on near real-time seismic moment tensor estimation in the regions of Indonesia, the Philippines, and Chile

Abstract

We have developed a near-field tsunami forecast system based on an automatic centroid moment tensor (CMT) estimation using regional broadband seismic observation networks in the regions of Indonesia, the Philippines, and Chile. The automatic procedure of the CMT estimation has been implemented to estimate tsunamigenic earthquakes. A tsunami propagation simulation model is used for the forecast and hindcast. A rectangular fault model based on the estimated CMT is employed to represent the initial condition of tsunami height. The forecast system considers uncertainties due to two possible fault planes and two possible scaling laws and thus shows four possible scenarios with these associated uncertainties for each estimated CMT. The system requires approximately 15 min to estimate the CMT after the occurrence of an earthquake and approximately another 15 min to make the tsunami forecast results including the maximum tsunami height and its arrival time at the epicentral region and near-field coasts available. The retrospectively forecasted tsunamis were evaluated by the deep-sea pressure and tide gauge observations, for the past eight tsunamis (M w 7.5-8.6) that occurred throughout the regional seismic networks. The forecasts ranged from half to double the amplitudes of the deep-sea pressure observations and ranged mostly within the same order of magnitude as the maximum heights of the tide gauge observations. It was found that the forecast uncertainties increased for greater earthquakes (e.g., M w > 8) because the tsunami source was no longer approximated as a point source for such earthquakes. The forecast results for the coasts nearest to the epicenter should be carefully used because the coasts often experience the highest tsunamis with the shortest arrival time (e.g., <30 min).

Faster Than Real Time Tsunami Warning with Associated Hazard Uncertainties

“…The detection and inversion of the seismic signal to constrain the earthquake's origin, magnitude and physical features is the first stage of a warning centre's workflow. Tsunami warning centres currently use a variety of techniques in this inversion stage (Melgar and Bock, 2013;Clément and Reymond, 2015;Inazu et al, 2016). After the seismic signal has been constrained, the second stage focuses on deducing the level of threat posed by the tsunamigenic event.…”

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

“…It mainly focused on generating a warning for the tsunamigenic earthquake that occurs at a distance from the site where the warning is issued. It is also critical to develop and examine the performance of the tsunami forecasting method for the coasts near the source where disastrous tsunami arrives within~30 min [e.g., Tsushima et al, 2009;Wei et al, 2013;Gusman et al, 2014;Maeda et al, 2015;Inazu et al, 2016;Yamamoto et al, 2016]. At present, there are not enough records which are observed at less than~100 km from the hypocenter or inside the focal area, although a few stations recorded tsunamis near the source region [e.g., Mikada et al, 2006;Maeda et al, 2011].…”

Assessment of GNSS-based height data of multiple ships for measuring and forecasting great tsunamis

“…Such methods are incorporated into operational systems of the Pacific Tsunami Warning Center (PTWC) PTWC/ITIC 2014), the French Polynesian Tsunami Warning Center (CPPT: Centre Polynésien de Prévention des Tsunamis) (Clément and Reymond 2015;Jamelot and Reymond 2015), and the National Research Institute for Earth Science and Disaster Resilience (NIED), Japan (Inazu et al 2016). These systems require 10-20 min to obtain a reliable seismic moment tensor solution of a tsunamigenic earthquake, and additional time to calculate the tsunami.…”