T-waves triggered by Chilean earthquakes recorded at CTBT-IMS station HA03

In addition to monitoring the oceans for signs of nuclear explosions, the International Monitoring System (IMS) hydroacoustic data have been used for a broad range of civil and scientific applications, including the study of submarine earthquakes. This presentation analyzes T-wave signals recorded at CTBT-IMS hydrophone station HA03 triggered by Chilean earthquakes between 2014 and 2022. HA03 is located in the Juan Fernández Islands (Chile, South-East Pacific Ocean); in particular, the hydrophone arrays are located approximately 15 km north (H03N) and 15 km south (H03S) of Robinson Crusoe Island to account for the acoustic shadow produced by the islands. Arrival time and back azimuth of the recorded T-waves were estimated using the Dase ToolKit - Graphical Progressive Multi-Channel Correlation (DTK-GPMCC) program. Different arrivals within the duration of the earthquake signals were identified. However, discrepancies between expected and measured back azimuths can be observed for H03N and H03S. A three-dimensional underwater acoustic model was utilized to determine the cause of these differences. Based on the hydroacoustic arrivals identified for the analyzed earthquakes, a discussion is provided on the conversion from seismic to acoustic waves (T-waves generation zone). Moreover, reflected propagation paths induced by bathymetric features along the path from the T-waves generation zone to H03N and H03S are discussed.