Tracking Typhoons Using Seismic Waveforms:  What have we Learned so far? 

Dr Wu-Cheng Chi (Institute of Earth Sciences, Academia Sinica)
[戚務正博士/中央研究院地球科學研究所]


Abstract
========

Typhoons inflict large damage to societies, but
are usually difficult to monitor in close proximity in realtime
without expensive instruments. Here we study the
possibility of using seismic waveforms on the seafloor and
on land to monitor the turning of a far away or approaching
typhoon. Up to 67% of the typhoons making landfall in
Taiwan come from the eastern shore, so that we deployed
broadband ocean-bottom seismometers (OBSs) offshore
eastern Taiwan in 2006 to study ground motion in close
proximity to a typhoon. Typhoons generate ocean waves,
which generate pressure signals in the water column before
being transmitted to the seafloor as seismic waves and
recorded by the OBSs. The ground motions on the seafloor
correlate with locally increased (ocean) wave heights and
wave periods, suggesting that the ground motions are
mostly induced by in situ or nearby pressure fields, as
shown by coherence function analyses. When a typhoon
turns and changes wave-wave interaction near the source
region, a new set of en echelon patterns develops which
can be observed by OBSs and land stations. Similar features
occur when a typhoon crosses a landmass and
re-enters the ocean. The energy level ratio between the
single-frequency and double-frequency microseisms also
changes abruptly when the typhoon turns. These features
can potentially help near real-time early warning with little
cost to complement other conventional typhoon early
warning methods.

 

References:

Chi, Wu-Cheng*, W.J. Chen, D. Dolenc, B.Y. Kuo, and D. Dolenc (2010) Seismic Monitoring of Western Pacific Typhoons, Marine Geophysical Researches, 31:239-251. DOI 10.1007/s11001-010-9105-x.


Chi, Wu-Cheng*, W.J. Chen, D. Dolenc, B.Y. Kuo, C.R. Lin, and J. Collins (2010) Seismological Report on the 2006 Typhoon Shanshan that Lits up Seismic Stations Along its Way, Seismological Research Letters, 81, 4, 592-596, doi: 10.1785/gssrl.81.4.592.