Abstract

We introduce a new data source of dense deep-ocean tsunami records from Ocean Bottom Pressure Gauges (OBPGs) which are attached to Ocean Bottom Seismometers (OBS) and apply them for far-field and near-field tsunami warnings. Tsunami observations from OBPGs are new sources of deep-ocean tsunami observations which, for the first time, provide dense tsunami data with spacing intervals in the range of 10–50 km. Such dense data are of importance for tsunami research and warnings and are capable of providing new insights into tsunami characteristics. Here, we present a standard procedure for the processing of the OBPG data and extraction of tsunami signals out of these high-frequency data. Then, the procedure is applied to two tsunamis of 15 July 2009 Mw 7.8 Dusky Sound (offshore New Zealand) and 28 October 2012 Mw 7.8 Haida Gwaii (offshore Canada). We successfully extracted 30 and 57 OBPG data for the two aforesaid tsunamis, respectively. Numerical modeling of tsunami was performed for both tsunamis in order to compare the modeling results with observation and to use the modeling results for the calibration of some of the OBPG data. We successfully employed the OBPG data of the 2012 Haida Gwaii tsunami for tsunami forecast by applying a data assimilation technique. Our results, including two case studies, demonstrate the high potential of OBPG data for contribution to tsunami research and warnings. The procedure developed in this study can be readily applied for the extraction of tsunami signals from OBPG data.

Highlights

  • We successfully employed the Ocean Bottom Pressure Gauges (OBPGs) data of the 2012 Haida Gwaii tsunami for tsunami forecast by applying a data assimilation technique

  • For two types of OBPG data, the Absolute seafloor Pressure Gauges (APG) give the absolute values of wave amplitude while Differential seafloor Pressure Gauges (DPG) give

  • The tsunami was recorded on Deep-Ocean Assessment and Reporting of Tsunami (DART) stations as well as on the dense array of OBPGs in the Cascadia subduction zone located about km from the earthquake source region

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Summary

Introduction and Background

Application of Dense Offshore Tsunami Observations from Ocean. B & W IN PRINT high sampling rates of 10–50 samples per second while DARTs record the tsunami waves with a rate of 1 record per 15 s at best, and (4) OBSs are deployed in large numbers (from *50 to *100) with spacing in the range 10–50 km (Fig. 1). Data from dense array of OBS pressure gauges provide several measurements per tsunami wavelength; can help to study spatial distribution of tsunamis. The amplitudes of the waves recorded by DPGs are larger than those recorded by neighboring DARTs and APGs. Figure 6 presents examples of DART, APG and DPG records of the 2012 Haida Gwaii tsunami and comparisons with simulated waveforms. This is because of the differential nature of the pressures recorded by the DPG instruments and the records need to be corrected. Research Institutions for Seismology Data Management Center (http://ds.iris.edu/mda/_OBSIP)

Methodology
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Conclusions

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