The earthquake events, which induce groundwater level
anomalies, issued by the TCWB were adopted. Most of the events
showed co- or post-seismic groundwater changes. The recovery
behavior generally followed a step change. Table 3 shows the frequency
of oscillatory and step changes of the groundwater level
from the 21 earthquake events at the eight observation wells.
Changes of oscillation were frequent whereas step changes were
observed in less than one third of the total observed changes.
Among the eight observation wells, Tunwei and Hualien were the most sensitive to earthquakes. Not all wells close to the epicenter
responded to the earthquakes. Wells far away from the epicenter
sometimes showed anomalous groundwater variations.