More Like this

1. Ross Ice Shelf Icequakes Associated With Ocean Gravity Wave Activity

   https://doi.org/10.1029/2019GL084123  

   Chen, Z.; Bromirski, P_D; Gerstoft, P.; Stephen, R_A; Lee, W_S; Yun, S.; Olinger, S_D; Aster, R_C; Wiens, D_A; Nyblade, A_A (August 2019, Geophysical Research Letters)

   Abstract Gravity waves impacting ice shelves illicit a suite of responses that can affect ice shelf integrity. Broadband seismometers deployed on the Ross Ice Shelf, complemented by a near‐icefront seafloor hydrophone, establish the association of strong icequake activity with ocean gravity wave amplitudes (A_G) below 0.04 Hz. The Ross Ice Shelf‐front seismic vertical displacement amplitudes (A_SV) are well correlated withA_G, allowing estimating the frequency‐dependent transfer function from gravity wave amplitude to icefront vertical displacement amplitude (T_GSV(f)).T_GSV(f) is 0.6–0.7 at 0.001–0.01 Hz but decreases rapidly at higher frequencies. Seismicity of strong icequakes exhibits spatial and seasonal associations with different gravity wave frequency bands, with the strongest icequakes observed at the icefront primarily during the austral summer when sea ice is minimal and swell impacts are strongest. 

   more » « less
2. Remote Triggering of Icequakes at Mt. Erebus, Antarctica by Large Teleseismic Earthquakes

   https://doi.org/10.1785/0220210027  

   Li, Chenyu; Peng, Zhigang; Chaput, Julien A.; Walter, Jacob I.; Aster, Richard C. (May 2021, Seismological Research Letters)

   null (Ed.)

   Abstract Recent studies have shown that the Antarctic cryosphere is sensitive to external disturbances such as tidal stresses or dynamic stresses from remote large earthquakes. In this study, we systematically examine evidence of remotely triggered microseismicity around Mount (Mt.) Erebus, an active high elevation stratovolcano located on Ross Island, Antarctica. We detect microearthquakes recorded by multiple stations from the Mt. Erebus Volcano Observatory Seismic Network one day before and after 43 large teleseismic earthquakes, and find that seven large earthquakes (including the 2010 Mw 8.8 Maule, Chile, and 2012 Mw 8.6 Indian Ocean events) triggered local seismicity on the volcano, with most triggered events occurring during the passage of the shorter-period Rayleigh waves. In addition, their waveforms and locations for the triggered events are different when comparing with seismic events arising from the persistent small-scale eruptions, but similar to other detected events before and after the mainshocks. Based on the waveform characteristics and their locations, we infer that these triggered events are likely shallow icequakes triggered by dilatational stress perturbations from teleseismic surface waves. We show that teleseismic earthquakes with higher peak dynamic stress changes are more capable of triggering icequakes at Mt. Erebus. We also find that the icequakes in this study are more likely to be triggered during the austral summer months. Our study motivates the continued monitoring of Mount Erebus with dense seismic instrumentation to better understand interactions between dynamic seismic triggering, crospheric processes, and volcanic activity. 

   more » « less
3. Discrimination between icequakes and earthquakes in southern Alaska: an exploration of waveform features using Random Forest algorithm

   https://doi.org/10.1093/gji/ggae106  

   Kharita, Akash; Denolle, Marine A; West, Michael E (March 2024, Geophysical Journal International)

   SUMMARY This study examines the feature space of seismic waveforms often used in machine learning applications for seismic event detection and classification problems. Our investigation centres on the southern Alaska region, where the seismic record captures diverse seismic activity, notably from the calving of marine-terminating glaciers and tectonic earthquakes along active plate boundaries. While the automated discrimination of earthquakes and glacier quakes is our nominal goal, this data set provides an outstanding opportunity to explore the general feature space of regional seismic phases. That objective has applicability beyond ice quakes and our geographic region of study. We make a noteworthy discovery that features rooted in the spectral content of seismic waveforms consistently outperform statistical and temporal features. Spectral features demonstrate robust performance, exhibiting resilience to class imbalance while being minimally impacted by factors such as epicentral distance and signal-to-noise ratio. We also conduct experiments on the transferability of the model and find that transferability primarily depends on the appearance of the waveforms. Finally, we analyse misclassified events and find examples that are identified incorrectly in the original regional catalogue. 

   more » « less