Source Process for Two Enigmatic Repeating Vertical‐T CLVD Tsunami Earthquakes in the Kermadec Ridge

Abstract

Two repeating compensated linear vector dipole (CLVD) earthquakes occurred in 2009 and 2017 on the Kermadec Ridge near the Curtis submarine volcano. The tsunami and seismic waveforms of both events are almost identical. Simulated tsunami and seismic waveforms are compared with observations of the 2017 event to estimate the location and geometry of the source. A CLVD source model at 8–14 km depth is consistent with the global CMT solution but generates no tsunami. The tsunami waveforms can be well reproduced if the source model is about 1.5 km deep. However, a seismic source at this depth is not consistent with the observed seismic waves. This suggests that two sources were involved with different depths. The main, shallow, tsunami source could be due to hydrofracturing of heated water in a shallow sediment layer triggered by a deeper earthquake.

Sub‐Decadal Volcanic Tsunamis Due To Submarine Trapdoor Faulting at Sumisu Caldera in the Izu–Bonin Arc

“…The submarine trapdoor faulting mechanism identified in this study may be categorized as a volcanic earthquake mechanism, but is characterized by large‐amplitude tsunamis without significant seismic radiation and by quasi‐regular recurrence. This mechanism may also explain unusual tsunamis with similar characteristics generated near volcanic islands in the Kermadec arc, north of New Zealand (Gusman et al., 2020). These volcanic tsunamis due to submarine trapdoor faulting suggest that continuous monitoring of submarine calderas is necessary to reliably assess tsunami hazards.…”

Sub-decadal Volcanic Tsunamis Due to Submarine Trapdoor Faulting at Sumisu Caldera in the Izu-Bonin Arc

“…The submarine trapdoor faulting mechanism identified in this study may be categorized as a volcanic earthquake mechanism, but is manuscript submitted to Journal of Geophysical Research: Solid Earth characterized by large-amplitude tsunamis without significant seismic radiation and by quasiregular recurrence. This mechanism may also explain unusual tsunamis with similar characteristics generated near the volcanic islands in the Kermadec Arc, north of New Zealand (Gusman et al, 2020). These volcanic tsunamis due to submarine trapdoor faulting suggest that continuous monitoring of submarine calderas is necessary to reliably assess tsunami hazards.…”

The 2021 Loyalty Islands Earthquake (Mw 7.7): Tsunami Waveform Inversion and Implications for Tsunami Forecasting for New Zealand

“…We used a finite fault approach (e.g., Hjörleifsdóttir et al., 2009; Holden et al., 2017) where a set of point sources represent the spatiotemporal evolution of slip on the faults. Synthetic seismograms were numerically well resolved down to 20 s. We used a dataset from a total of 21 stations to quantify the model accuracy by a data‐synthetic misfit defined as $$${\chi }_{full}=\sum \frac{{\vert d-s\vert }^{2}}{\vert d\vert \vert s\vert }$$$ where $$s$$ and $$d$$ are the amplitude of the vertical component of observed and synthetic displacement seismogram, respectively, and the summation was performed over all stations (e.g., Gusman, Kaneko, et al., 2020). To consider an alternative misfit quantification, we also report peak amplitude misfit defined as $$${\chi }_{peak}=\sum \frac{{\vert \mathrm{max}(d)-\mathrm{max}(s)\vert }^{2}}{\vert \mathrm{max}(d)\vert \vert \mathrm{max}(s)\vert }$$$ Here we evaluate our static slip distribution estimated from the tsunami data using seismic wave simulations.…”