TITLE:
Seismic Tremors and Their Relation to Cryosphere Dynamics in April 2015 around the Lützow-Holm Bay, East Antarctica
AUTHORS:
Masaki Kanao, Takahiko Murayama, Masa-Yuki Yamamoto, Yoshiaki Ishihara
KEYWORDS:
Seismic Tremors, Ice Shocks, Cryosphere Dynamics, Sea-Ice, Icebergs, Lützow-Holm Bay, Antarctica
JOURNAL NAME:
International Journal of Geosciences,
Vol.8 No.8,
August
30,
2017
ABSTRACT: Characteristics and statistics of seismic tremors occurring during April 2015
were investigated by using short-period and broadband seismographs deployed
at Syowa Station (SYO), in the Lützow-Holm Bay (LHB), East Antarctica.
In order to examine a relationship between surface environments in particular
cryosphere variation, the MODIS satellite images were utilized for
comparison with the detected tremor events. Since a large volume of sea-ice
was discharged during the April, together with several large icebergs passed
through from the west to the east at northern edge of the fast sea-ice of LHB,
it was expected to detect seismic tremors involving cryospehre dynamics.
During the month, a total number of 49 tremor events including short duration
ice shocks were identified. Majority of the events (N = 39) had their duration
times more than 15 minutes, which were divided into both tremors and ice
shocks on the basis of experienced definition at SYO. Cryospheric sources
recorded by seismic tremors were classified into several origins (collision,
calving, crevassing, crashing, etc.): “crevassing events” along the large cracks
inside the fast sea-ice in LHB (04 April), “discharge events” of fast sea-ice
from the Bay (07 April), “collision events” between iceberg and the edge of
fast sea-ice (14 April), “crashing movement” between fragmentation of fast
sea-ice and packed sea-ice (18 April), and other origins. In particular, strong
amplitude tremors with harmonic overtones were assumed to be occurred independently
from whether condition, because these overtone tremors were
identified at less stormy days by comparison with infrasound data at SYO.