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

Abstract

Shear strains, among other ground motions, can be induced by weather‐related processes. As a result, broadband seismic data offer a unique tool for understanding these natural weather events. Here we used continuous seismic, meteorological, and stream data to analyze weather‐related ground motions during typhoons and rainy seasons in Taiwan. In addition to high‐frequency signals, we detected ultralong period seismic signals at the station Mahsi (MASB) during three meteorological events: Typhoon Kalmaegi in 2008, Typhoon Morakot in 2009, and the East Asian rainy season in 2012. Seismic velocity signals with frequencies lower than 0.3 mHz correlate with precipitation and with the time derivative of the water level in a nearby river. We converted the seismic signals to ground tilt and found that the tilt correlates with the time history of river water level, which fluctuates with precipitation. The seismically derived tilt ranges from 10−8 to 10−7 radians, consistent with an analytic circular loading model, indicating water level fluctuations of higher than 1 m in the small river 30 m away from MASB. To quantify precipitation using seismic data, we successfully modeled seismic waveforms using an empirical Green's function method, which gives good fits to both main event seismic waveforms and precipitation time history. This work demonstrates that continuous recordings from broadband seismometers may help determine local fluvial water load and could be useful for decadal rainfall change research.

A Seismic Approach to Flood Detection and Characterization in Upland Catchments

“…We attribute this pattern of systematic particle motion, which was not recorded at other seismic stations in the region (Supporting Information S1), to surface tilt due to a large, mobile mass, approaching the station from the southwest, passing it to the south and then moving off toward the east. Other studies (Yang et al, 2018) have reported a similar tilt signal due to the surface load of a flooding river at several km distance. Hence, a clear tilt trajectory can be a first order indicator of a propagating flood (Figure 1c), if it evolves progressively over time, the source moves along a channel and is within a sensible distance of the seismometer, and the pattern is not visible at other stations outside the sensitive range.…”

“…For a seismic synopsis, particle motion analysis was performed for the time period 2021‐07‐14 10:00:00 to 22:10:00 UTC. The raw seismic data with 100 Hz sampling frequency, downloaded via FDSN data services were deconvolved, low pass filtered at 0.0001 Hz (Yang et al., 2018) and plotted on the horizontal plane. The seismic spectrogram was calculated from the unfiltered signal for the same time interval, using a 30 s window with 80% overlap, smoothed by a 15 s subwindow also with 80% overlap.…”

“…Seismometers installed at safe distance from flooding river channels are sensitive to several flood parameters such as water level, discharge, and event propagation velocity (Cook et al, 2018(Cook et al, , 2021Goodling et al, 2018;Yang et al, 2018). They record ground motion signatures of river processes like turbulence-driven force fluctuations and bedload particle impacts on the river bed, superimposed on numerous other seismic signals.…”

Deep sea floor observations of typhoon driven enhanced ocean turbulence

“…The turbulence duration may be concluded from the OBS-C of which values are enhanced for several hours during the largest convection around day 258. OBS-C waveforms may contain both translational and rotational ground motions (Yang et al, 2018). These observations cannot be attributed to both seismic earthquake activity and infra-gravity ocean surface wave activity because here we studied much longer period signals, and also because energy propagated with much slower apparent speeds O(0.1) m s -1 .…”

Different Couplings Between Precipitation and Deformation at the Same Site: A Case Study at Central Pyrenees (Spain)

“…Studies of hydrogeophysical processes are not numerous and rely on considerable simplifications, mainly because of the lack of knowledge about local geology and hydrogeology. Some articles deal with signatures of rainfalls on seismic (e.g., Díaz et al., 2014; Yang et al., 2018) and deformation (e.g., Braitenberg et al., 2019; Devoti et al., 2015; Lesparre et al., 2017) records, others with signatures of anthropogenic activities such as fluid injection and extraction (e.g., Atkinson et al., 2020; Barbour & Wyatt, 2014; Jahr et al., 2008; Schuite et al., 2017). Díaz et al.…”