일본 지진을 연구하는 과학진은 목요일에 발표하는데, 아주 진기한 지구 진동을 처음으로 감지했다는
것이다. 그들은 먼곳의 강력한 폭풍을 추적한다. 이를 통해서 전문가들은 지구의 내부구조를 좀더 알게되는데, 지진과 해양의 폭풍을 감지하는걸 개선한다.
Miami (AFP) - Scientists who study earthquakes in Japan
said Thursday they have detected a rare deep-Earth tremor for the first time and
traced its location to a distant and powerful storm.
The findings, published in the US journal Science, could
help experts learn more about the Earth's inner structure and improve detection
of earthquakes and oceanic storms.
북대서양의 폭풍은 "기상 폭탄" 이라고 알려졌는데, 작지만 잠재성이 있는 폭풍은 압력을 끌어모으는 것이다. 폭풍이 불고 있을때 해저 해분에는 파도들이 불어치고, 해분을 두드린다, 이것은 그린란드와 아이슬란드를 타격한다.
지상의 지진계와 해분의 지진계를 사용해서 이전에 감지하지 못한 이상한 것을 발견한느데, 에스파라 불리는 마이크로 수준의 지진파 진동이다. 마이크로 지진파는 아주 약한 진동이다.
피파 P waves로 알려진 것과 다른 에스파는 대형 허리케인이 불때 감지되곤 한다. 피파가 빠르게 움직이는데, 동물은 지진이 오기전에 이것을 감지한다. 감지가 어려운 에스파는 2차 지진파로써 더 느리게 오며 액체를 투과하지 못하고 고체를 통해 전달된다. 사람들은 지진이 발생할때만 에스파를 느낀다.
The storm in the North Atlantic was known as a "weather
bomb," a small but potent storm that gains punch as pressure quickly
mounts.
Groups of waves sloshed and pounded the ocean floor
during the storm, which struck between Greenland and Iceland.
Using seismic equipment on land and on the seafloor that
usually detects the Earth's crust crumbling during earthquakes, researchers
found something they had not detected before -- a tremor known as an S wave
microseism.
Microseisms are very faint tremors.
Another kind of tremor, known as P waves, or primary
wave microseisms, can be detected during major hurricanes.
P waves are fast-moving, and animals can often sense
them just before an earthquake hits.
The elusive S waves, or secondary waves, are slower, and
move only through rock, not liquid. Humans feel them during
earthquakes.
Using more than 200 stations operated by the National
Research Institute for Earth Science and Disaster Prevention in Japan's Chugoku district,
researchers Kiwamu Nishida and Ryota Takagi "successfully detected not only P
wave microseisms triggered by a severe and distant North Atlantic storm, known
as a weather bomb, but also S wave microseisms, too," said the study.
"The discovery marks the first time scientists have
observed... an S wave microseism."
Microseism S waves are so faint that they occur in the
0.05 to 0.5 Hz frequency range.
The study in the journal Science details how researchers
traced the direction and distance to the waves' origins, and the paths they
traveled.
이런 0.05 에서 0.5 Hz 에스파를 감지할수있으므로써 지구이 깊은 구조를 연구할수있게 되었다고 피터 걸스토프트와 피터 브로밀스키, 캘리포니아 대학 연구진은 기록했다.
The discovery "gives seismologists a new tool with which
to study Earth's deeper structure," said Peter Gerstoft and Peter Bromirski of
the University of
California, San Diego in an accompanying Perspective article.
Learning more about microseismic S waves may "add to our
understanding of the deeper crust and upper mantle structure."