Characteristics of Seismic Wave Propagation of Harmonic Tremors Observed at the Margin in the Lützow-Holm Bay, East Antarctica

Several kinds of seismic signals involving physical interactions within the shallow atmosphere—ocean—cryosphere—solid earth system have been detected in continental margins of Antarctica and surrounding Southern Ocean. In this study, characteristic features of seismic tremors with harmonic overtones recorded at Syowa Station, the Lützow-Holm Bay (LHB), East Antarctica, are demonstrated for the period from October 2014 to March 2015. A few tens of tremors (N = 81) are identified in both the short-period and broadband seismographs. The characteristic tremors with harmonic overtones can be explained by a repetitive source, suggesting the existence of several interglacial asperities. It implies that the tremors might be involved in local origins, presumably be the dynamics of cryosphere, including discharge of sea-ices from bay, collision of icebergs and fast-ices, calving of glaciers, and the other origins. The strong harmonic tremors with frequency overtones found in LHB are mostly generated by collisions between icebergs and the edge of fast sea-ice by comparison with satellite data. Seismic tremors in terms of cryosphere dynamics, therefore, are likely to be associated with variation of surface environment in the Antarctic, and continuous monitoring of their time-space variability provides indirect evidence of climate change

A New Trend in Cryoseismology: A Proxy for Detecting the Polar Surface Environment

“Cryoseismology” is a new branch of interdisciplinary science, which treats glacier-related seismic events and their dynamics associated with the variable phenomenon of the Earth’s surface. Cryoseismology is considered to be one of the proxies for detecting environmental variations, particularly in the polar region, which contains the majority volume of the cryosphere of the planet. Various kinds of cryoseismic signals recently reported are reviewed by classifying them into several categories on the basis of their occurrence locations and focal dynamics. Temporal-spatial variations in cryoseismic activities and their wave propagation characteristics could demonstrate a new image of cryodynamics, which have not yet been known well before but have a significant impact on the global environment and human activities

Seismic Detection in the Inland Plateau of East Antarctica

Several international programs to deploy broadband seismic stations over the Antarctic continent were conducted during the International Polar Year (IPY 2007–2008). Antarctica’s Gamburtsev Province (AGAP)/Gamburtsev Mountains Seismic Experiment (GAMSEIS), which was a part of AGAP and the Polar Earth Observing Network (POLENET), contributed greatly to establish a geophysical network in Antarctica. AGAP/GAMSEIS was an internationally coordinated deployment of more than 30 seismographs over the crest of the Gamburtsev Mountains and the areas of Dome-A, -C, and -F. The project provided a detailed information on the crust and mantle structures and, key constraints on the origin of the Gamburtsev Mountains and more broadly on the structure and evolution of the East Antarctic craton and subglacial environment. With the data from GAMSEIS and POLENET, the local and regional seismic signals associated with ice movements, oceanic loadings, and local meteorological variations were recorded in addition to a number of teleseismic events around the globe. The characteristic seismic signals of local origin in the inland plateau of the ice sheet were demonstrated with a capability to investigate subglacial environment, particularly at the marginal areas of the East Antarctic continent

Summary: Global Seismology and the Polar Region

“Polar Seismology” has been developed since the International Geophysical Year (IGY 1957–1958) and contributed significantly to global seismology in particular through the big project of the International Polar Year (IPY 2007–2008). At present, in the first stage of the twenty-first century, “polar regions” play an important role to monitor and understand the drastic variations in the Earth’s system as well as to advance the inter-disciplinary studies of the interactions among multispheres within the system

A Decade of Advances in Cryoseismology

Among the various kinds of seismological features observed in the polar region, the characteristics of the wavelets and involved seismicity related to cryosphere dynamics are introduced to mark a decade of advances in “cryoseismology.” Classifying the seismic waves originating from the cryosphere dynamics and understanding the generating mechanism as well as the temporal-spatial distributions in seismicity should be important in order to realize surface environmental variations associated with global warming in the polar region

Introduction: Progress of Seismology in Polar Region

Several kinds of seismological investigations have been conducted in the polar region, which include the areas of both the Arctic and the Antarctic regions, in various depth ranges from the surface layers to the deep interiors of the Earth. The polar region has an advantage in order to seek inside the physical condition of the Earth as a “window” viewed from high latitudes. In this chapter, historical issues and progress of seismic research and its observations in the polar region are demonstrated during the last half-century from the era of the International Geophysical Year (IGY 1957–1958)

Structural Studies on the Earth’s Crust, Plates, and the Ice Sheet in the Polar Region

During the International Polar Year (IPY 2007–2008), a number of seismological studies regarding the structure and dynamics of the Earth’s surface layers, the static inner structure of the crystalline crust and lithosphere involving Earth’s history, earthquake occurrence mechanism, inner deformation of the plates, crustal movement relating to deglaciation, seismic isotropy, and the other topics of the ice sheet overlying the solid earth were conducted. In this chapter, recent seismological results as for the structural study of the crust, plates, and ice sheet in bipolar regions are overviewed

Studies on Seismicity in the Polar Region

During the International Polar Year (IPY 2007–2008), several seismological research studies have been conducted as a part of geophysical observations in bipolar regions. In this chapter, recent studies involving seismicity in bipolar regions are introduced on the basis of compiled data from the International Seismological Centre (ISC). The relationship between the present seismicity and the heterogeneous structure of the crust and upper mantle is discussed, together with a review of geoscientific achievements in terms of the tectonic history of the Earth