Abstract

In the days following the January 12, 2010 Mw 7 Haiti earthquake the shaking intensity near the epicenter was overestimated and the spatial extent of the potentially damaging shaking was underestimated. This was due to the lack of seismometers in the near-source region at the time of the earthquake. Besides seismic waves, earthquakes generate infrasound, i.e., inaudible acoustic waves in the atmosphere. Here we show that infrasound signals, detected at distant ground-based stations, can be used to generate a map of the acoustic intensity, which is proportional to the shaking intensity. This is demonstrated with infrasound from the 2010 Haiti earthquake detected in Bermuda, over 1700 km away. Wavefront parameters are retrieved in a beamforming process and are backprojected to map the measured acoustic intensity to the source region. The backprojection process accounts for horizontal advection effects due to winds and inherent uncertainties with regard to the time of detection and the back azimuth resolution. Furthermore, we resolve the ground motion polarity in the epicentral region and use synthetics generated by an extended infrasound source model to support this result. Infrasound measurements are conducted globally for the verification of the Comprehensive Nuclear-Test-Ban Treaty and although the network was designed to provide global coverage for nuclear explosions in the atmosphere, it is shown in this paper that there is also global coverage for the estimation of acoustic shaking intensity. In this study, we lay the groundwork that can potentially make infrasound-based ShakeMaps a useful tool alongside conventional ShakeMaps and a valuable tool for earthquake disaster mitigation in sparsely monitored regions.

Highlights

  • The January 12, 2010 Mw 7 Haiti earthquake is one of the most devastating earthquake disaster in recent history

  • Characteristic wavefront parameters are extracted in the beamforming process, namely, the direction of arrival back azimuth (BAZ), the speed of horizontal propagation over the array apparent velocity (AV), and the signal coherency in terms of signal-to-noise ratio (SNR) (Fig. 3c-e, respectively)

  • As a detection window in time is mapped to a detection patch in space, this value is used to estimate the acoustic intensity associated with the part of the signal that was contributed by that patch

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Summary

Introduction

The January 12, 2010 Mw 7 Haiti earthquake is one of the most devastating earthquake disaster in recent history. Much scientific work has been carried out in Haiti following the 2010 earthquake disaster Backprojections of infrasonic signals from earthquakes (Shani-Kadmiel et al, 2018) and nuclear explosions (Assink et al, 2018) provide insight into the seismo-acoustic coupling process and can map the distribution of the epicentral and secondary sources of infrasound. Seismic signals were not measured in Haiti during the 2010 earthquake, infrasound was generated over the region and was detected by an International Monitoring System (IMS) array IS51 on Bermuda island, 1738 km away (Fig. 2). This observation is supported by a simulation of an extended infrasound source using the Rayleigh integral (Fig. 6)

Data acquisition and beamforming results
Seismo-acoustic coupling and propagation from Haiti to Bermuda
From detections in time to acoustic intensity map
Discussion and conclusions

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