Two Volcanic Tsunami Events Caused by Trapdoor Faulting at a Submerged Caldera Near Curtis and Cheeseman Islands in the Kermadec Arc
Two submarine earthquakes (M_w 5.8) occurred near volcanic islands, Curtis and Cheeseman, in the Kermadec Arc in 2009 and 2017. Following both earthquakes, similar tsunamis with wave heights of about a meter, larger than expected from their moderate seismic magnitudes, were observed by coastal tide gauges. We investigate the source mechanism for both earthquakes by analyzing tsunami and seismic data of the 2017 event. Tsunami waveform analysis indicates that the earthquake uplifted a submerged caldera around the islands. Combined analysis of tsunami and seismic data suggests that trapdoor faulting, or sudden intra-caldera fault slip interacted with magma reservoir deformation, occurred due to magma overpressure, possibly in association with caldera resurgence. The earthquake scaling relationship for trapdoor faulting events at three calderas deviates from that for regular earthquakes, possibly due to the fault-reservoir interaction in calderas.
© 2023. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. We thank Editor, Christian Huber, and Falk Amelung and an anonymous reviewer for constructive suggestions. We thank Zhongwen Zhan for helpful discussion. This study is funded by the JSPS (Japan Society for the Promotion of Science) KAKENHI (JP17J02919, JP20J01689, and JP19K04034), by the JST (Japan Science and Technology Agency) J-RAPID (JPMJJR1805). Osamu Sandanbata's travel to California Institute of Technology was supported by Oversea Internship Program of Earthquake Research Institute, the University of Tokyo. Data Availability Statement: The tide-gauge data are available from Land Information New Zealand (LINZ; https://www.linz.govt.nz/sea/tides/sea-level-data/sea-level-data-downloads). The topography and bathymetry data are available from GEBCO Compilation Group through the British Oceanographic Data Centre (Weatherall et al., 2015; https://www.gebco.net/data_and_products/gridded_bathymetry_data/gebco_30_second_grid/), the National Institute of Water and Atmospheric Research in New Zealand (NIWA; https://niwa.co.nz/our-science/oceans/bathymetry), and LINZ (https://data.linz.govt.nz/). The seismic data are available through the Data Management Center of the Incorporated Research Institutions for Seismology (IRIS)'s Wilber 3 system (https://ds.iris.edu/wilber3/) or IRIS Web Services (https://service.iris.edu/), including the seismic networks of IU (GSN; Albuquerque Seismological Laboratory, 1988), AU (ANSN; H., G., & Geoscience Australia, 2021), NZ (New Zealand National Seismograph Network), and G (GEOSCOPE; IPGP & EOST, 1982). The earthquake information is available from the GCMT catalog (Ekström et al., 2012; https://www.globalcmt.org/https://www.globalcmt.org/), or UGSG (https://earthquake.usgs.gov/ https://earthquake.usgs.gov/). The W-phase package (Duputel et al., 2012; Hayes et al., 2009; Kanamori & Rivera, 2008) is available through the website of W Phase source inversion (http://eost.u-strasbg.fr/wphase/index.html). We plotted focal mechanisms representing moment tensors with a MATLAB code developed by James Conder (available from https://www.mathworks.com/matlabcentral/fileexchange/61227-focalmech-fm-centerx-centery-diam-varargin). The best-fit source model presented in this paper is contained in Data Set S1, which is available from Zenodo (https://doi.org/10.5281/zenodo.7502680).
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