Earthquake

Magnetogravimetric study on the Scotia Plate, in the South Atlantic Ocean for the characterization of tsunamis

Arecco Alejandra

Universidad de Buenos Aires, Facultad de Ingeniería, Instituto de Geodesia y Geofísica Aplicadas

DOI: https://doi.org/10.59429/ear.v2i1.1880

Keywords: earthquakes; tsunamis; geomagnetic field; 2D gravimetric model; South Atlantic Ocean

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Abstract

The marine and coastal environments of the Scotia Sea regions in the Southern Atlantic Ocean and Antarctica are vulnerable to the potentially disastrous effects from seismic activity in the Scotia Arc. This paper presents a magnetogravimetric study of the Scotia Plate for tsunami characterization. The influence of earthquakes on the Geomagnetic Field (GMF) is investigated using data from INTERMAGNET network observatories.  A tectonic model from gravimetric data is evaluated using gravity data from NOAA and seismic refraction data from Lamont-Doherty Earth Observatory oceanic surveys. The study also assesses the impact on water level (WL) measured at 6 tide gauge stations in the region obtained from the Intergovernmental Oceanographic Commission (IOC). The WL records collected are filtered and analyzed to identify tsunamis at each station. Cross Wavelet Transform (XWT) is applied, and a frequency analysis of the GMF is conducted to identify specific frequencies during seismic events. A 2D tectonic model is constructed for the North Scotia Ridge using gravimetric and seismic data to characterize structural boundaries that may be activated during seismic events. The results reveal anomalous frequencies in the GMF horizontal component frequency analysis during the November 25, 2013 earthquake, those results shown great data correlation with [1;1.5] hour periods from different observatories in the study area. Gravimetric modeling delineates faults activated during seismic activity and edges of structures potentially activated due to the margin transcurrent and compressional nature. WL anomalies up to 1.30 m are obtained following earthquakes with a Richter scale magnitude greater than 8 Mw. The tsunami propagation speed in the study area averaged 460 km/h, consistent with the expected speed for those depths, except for Puerto Argentino (PA), which exceeded them by 50%.

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