Abstract
Several kinds of natural source signals are recorded by seismic exploration stations on the continental ice sheet in Eastern Dronning Maud Land, East Antarctica, during 2002 austral summer. They include not only tectonic earthquakes, but also ice-related phenomena possibly involving recent global climate change. The recorded signals are classified into (1) teleseismic events, (2) local ice quakes, and (3) unidentified events (X-phases). The teleseismic waves show the high signal-to-noise ratio in spite of the small magnitude of the event; this indicates that it is highly feasible to study not only the local shallow structure but also the deep structure of the earth by using teleseismic events. Frequency spectra of the all waveforms represent discordances along the observation seismic profile. The abrupt change of topography in the valley along the seismic profile might cause both the anomalous frequency content and travel times. Finally, an origin of the X-phases is speculated as the intraplate earthquakes or possibly large ice-quakes (glacial earthquakes) around Antarctica, involving global warming appeared in polar region.
Highlights
It was generally understood by a majority of seismologists in the IGY era that no extreme earthquakes occurred in the Antarctic
The origin of unknown characteristic phases is treated by focusing on the relationship with recent dynamics of ice-related phenomena, climate changes appearing in polar region, as well as the hidden microseismic activities around the Antarctic
The teleseismic events shown in the map are the same listed in Table 1, and an expanded local map of the studied area on the Mizuho Plateau, East Antarctica, is inserted on the same figure
Summary
The SEAL-2002 experiment recorded the artificial waveforms originated by seven large explosions with 161 temporary stations along the transect profile, which is almost parallel with the coast of the Lutzow-Holm Bay [11] They determined the P-wave velocity structure of the crust and upper mantle as well as the overlying ice sheet by seismic travel time analysis. A plausible possibility of low P-wave velocity appeared in the valley is explained by the presence of water infilling the area [14], which produces less reflections by radioecho sounding These phenomena are reported as the existence of a significant number of subglacial lakes in wide area of inland Antarctic continent [15, 16]. The origin of unknown characteristic phases is treated by focusing on the relationship with recent dynamics of ice-related phenomena (including glacial earthquakes), climate changes appearing in polar region, as well as the hidden (uninvestigated) microseismic activities around the Antarctic
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