Seismic monitoring of western Pacific typhoons

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.

Seismically Detected Ground Tilts Induced by Precipitation and Fluvial Processes: An Example From Taiwan

“…The frequency bands of offshore storm‐related signals are lower than 1 Hz: Wind from storms can transfer energy and generate ocean gravity waves to excite both short‐period double frequency (0.20–0.45 Hz) microseisms locally and long‐period double frequency (0.085–0.20 Hz) microseisms near coastlines at distant locations (Bromirski et al, ; Lin et al, ). Seafloor ground motion was also recorded by broadband ocean bottom seismometers when a typhoon passed over the western Pacific Ocean (Chi, Chen, Kuo, & Dolenc, ). When typhoons pass over the ocean and generate waves and surges, the changes in water column height and wave‐wave interaction induce pressure changes on the seafloor and the seabed responds accordingly (Yamamoto & Torii, ).…”

“…When typhoons pass over the ocean and generate waves and surges, the changes in water column height and wave‐wave interaction induce pressure changes on the seafloor and the seabed responds accordingly (Yamamoto & Torii, ). The seismic energy levels, dispersion patterns, and the polarization degrees of the seismic signals may also change when a typhoon changes direction (Chi, Chen, Kuo, & Dolenc, ; Chi, Chen, Dolenc, et al, ; Sufri et al, ).…”

Tracking major storms from microseismic and hydroacoustic observations on the seafloor

“…They are clearly associated with winter storms in both hemispheres [e.g., Ardhuin et al, 2011;Reading et al, 2014] and have been numerically modeled [e.g., Stutzmann et al, 2012;Gualtieri et al, 2014]. A few observations of storms have already been achieved either by individual seismometers on the seafloor [e.g., Latham et al, 1967;Chi et al, 2010] or by small-scale ocean bottom seismometer (OBS) networks [e.g., Lin et al, 2014]. Here we present the first investigation of secondary microseismic noise recorded on the seafloor by a large-scale, broadband seismological network while a cyclone was passing over it.…”

Multisensor, Microseismic Observations of a Hurricane Transit Near the ALOHA Cabled Observatory

“…Davy et al () and Davy et al () show observations of microseisms and ocean swell generated by tropical cyclones around Reunion Island in the Indian Ocean. In the 2F microseism band (3–10 s), normally attributed to the interaction of broadly directional waves directly from typhoons, Davy et al () found lower frequency microseisms (7–10 s) attributed to the interaction of a swell with its own coastal reflection (compare with results of Chi et al, , in prior paragraph). In one instance (during Tropical Cyclone Dumille in January 2013), Davy et al () describe the interaction between waves from the nearby Tropical Cyclone Dumille, with waves generated by a distant extra‐tropical storm in the Southern Indian ocean.…”