Tectonomagmatic activity and ice dynamics in the Bransfield Strait back‐arc basin, Antarctica

Abstract

[1] An array of moored hydrophones was used to monitor the spatiotemporal distribution of small-to moderate-sized earthquakes and ice-generated sounds within the Bransfield Strait, Antarctica. During a 2 year period, a total of 3900 earthquakes, 5925 icequakes and numerous ice tremor events were located throughout the region. The seismic activity included eight space-time earthquake clusters, positioned along the central neovolcanic rift zone of the young Bransfield back-arc basin. These sequences of small magnitude earthquakes, or swarms, suggest ongoing magmatic activity that becomes localized along isolated volcanic features and fissure-like ridges in the southwest portion of the basin. A total of 122 earthquakes were located along the South Shetland trench, indicating continued deformation and possibly ongoing subduction along this margin. The large number of icequakes observed show a temporal pattern related to seasonal freeze-thaw cycles and a spatial distribution consistent with channeling of sea ice along submarine canyons from glacier fronts. Several harmonic tremor episodes were sourced from a large ($30 km 2 ) iceberg that entered northeast portion of the basin. The spectral character of these signals suggests they were produced by either resonance of a small chamber of fluid within the iceberg, or more likely, due to periodicity of discrete stick-slip events caused by contact of the moving iceberg with the seafloor. These pressure waves appear to have been excited by abrasion of the iceberg along the seafloor as it passed Clarence and Elephant Islands.

Volcano‐Tectonic Activity at Deception Island Volcano Following a Seismic Swarm in the Bransfield Rift (2014–2015)

“…In the past decades, a few detailed studies have revealed a significant background of low-magnitude microseismicity around the Bransfield rift (Dziak et al, 2010;Ibáñez et al, 1997;Pelayo & Wiens, 1989;Robertson-Maurice et al, 2003). Despite the poor permanent station coverage, the International Seismological Center (ISC) catalog (ISC, 2017) comprises ∼200 earthquakes with magnitudes above ∼4.0 since 1960.…”

Seismicity in the Antarctic Continent and Surrounding Ocean

“…Similar cryoseismic phenomena have also been reported around the Ross Sea region (MacAyeal et al, 2009), the marginal sea of the Antarctic Peninsula [33], as well as the continental margin of Dronning Maud Land [17]. In particular, iceberg-originated harmonic tremor emanating from tabular icebergs was observed by both seismo-acoustic and local broadband seismic signals [35].…”

“…The so-called "ice-micity" detected around the Bransfield Strait and Drake Passage by a local network of hydrophone arrays in 2006-2007 illustrate the dynamic behavior of sea ice in the Bransfield and Antarctic Peninsula regions [33].…”

Characteristic atmosphere–ocean–solid earth interactions in the Antarctic coastal and marine environment inferred from seismic and infrasound recording at Syowa Station, East Antarctica

“…Seismic signals involving ice-related phenomena are called 'ice-quakes' (ice-shocks for smaller ones), and are most frequently reported in association with glacier-related mass movements of ice sheets, or with sea-ice, tide-cracks and icebergs (Anandakrishnan & Alley 1997;Kanao & Kaminuma 2006;Wiens 2007;Nettles & Ekström 2010). The so-called 'ice-micity' detected around the Bransfield Strait and Drake Passage by a local network of hydrophone arrays in 2006-2007 illustrated the dynamic behaviour of sea-ice in the Antarctic Peninsula (Dziak et al 2009). Local seismicity around the Lützow-Holm Bay was reported by Kanao & Kaminuma (2006), who detected 17 events using a local network deployed around the Bay.…”

“…7) and the Pan-Antarctic Observations System under the Scientific Committee on Antarctic Research. Hydroacoustic observations contribute to the understanding of wave-propagation inside the ocean, and have already been exploited to investigate seismicity and sea-ice dynamics around the Bransfield Strait, Antarctic Peninsula (Dziak et al 2009). The combination of seismic, infrasound and hydroacoustic observations is most likely required to understand in more detail the atmosphere -oceancryosphere-solid earth system and its variations with time.…”