Haru Matsumoto | Geology Reports

USGS2021

A Year-long Hydroacoustic Survey of the Mariana Islands Region

The Mariana Islands region hosts interesting geological features as well as abundant biodiversity. The subduction zone and back-arc spreading center have led to active volcanism that can have impacts on local islanders, aircraft flying in the region, and military activities. We deployed a small aperture hydrophone array from June 2017 to June 2018 in the Marianas back-arc to better characterize submarine volcanic activity in the region. In addition, we recorded other activity, including calls from historically understudied Bryde’s whales and T-phases from earthquakes. Here, we describe and discuss preliminary results from the array.

Conference Paper↗

USGS2019

Hydroacoustic, meteorologic and seismic observations of the 2016 Nansen Ice Shelf calving event and iceberg formation

On 7 April 2016, the Nansen Ice Shelf (NIS) front calved into two icebergs, the first large-scale calving event in >30 years. Three hydrophone moorings were deployed seaward of the NIS in December 2015 and over the following months recorded hundreds of short duration, broadband (10-400 Hz) cryogenic signals, likely caused by fracturing of the ice-shelf. The majority of these icequakes occur between January and early March 2016, several weeks prior to the calving observed by satellite on 7 April. Barometric pressure and wind speed records show the day the icebergs drifted from the NIS coincided with the largest low-pressure storm system recorded in the previous 7 months. A nearby seismic station also shows an increase in low-frequency energy, harmonic tremor, and microseisms on 7 April. Our interpretation is the northern segment of the NIS leading edge broke free during mid-January to February, producing high acoustic energy, but the icebergs remained stationary until the combination of a strong low-pressure system, with high winds freed the icebergs. As the unpinning of Antarctic ice shelves is not a well-documented process, our observations show that storm systems may play an under-appreciated role in Antarctic ice shelf break-up.

Frontiers in Earth Science↗