Streamflow Changes in the Vicinity of Seismogenic Fault After the 1999 Chi–Chi Earthquake

Abstract

Abstract-Changes in streamflow have been observed at 23 stream gauges in central Taiwan after the 1999 M W 7.6 Chi-Chi earthquake. Post-earthquake increases, ranging from 58 to 833% in discharge, were recorded at 22 gauges on four rivers and their tributaries. The streamflow increase typically peaked in 2-3 days and followed by a slow decay for a month or more. An increased groundwater discharge to the river after the earthquake can be attributed to rock fracturing by seismic shaking as well as pore pressure rise due to compressive strain. A large decrease in discharge was recorded immediately after the earthquake at the gauge near the earthquake epicenter. Further analysis of long-term data indicates that the post-earthquake discharge at the gauge reduced to a level smaller than that at an upstream gauge for 8 months. Such a streamflow decrease might have been caused by a discharge to the streambed due to a co-seismic decrease in pore pressure induced by crustal extension during the rupture of the thrust fault.

SAR and optical images correlation illuminates post-seismic landslide motion after the Mw 7.8 Gorkha earthquake (Nepal)

“…Many observations show co- or post-seismic variations of groundwater levels in wells 14 , 40 , 41 , stream-flow changes following earthquakes 42 , or fluid and fluxes changes as well as water temperature changes in hot springs 43 . In particular, very high magnitudes of groundwater level changes have been observed in the near-field of large earthquakes 40 , 41 , that can overpass by far the magnitudes of groundwater variations created by monsoons 42 .…”

“…Many observations show co- or post-seismic variations of groundwater levels in wells 14 , 40 , 41 , stream-flow changes following earthquakes 42 , or fluid and fluxes changes as well as water temperature changes in hot springs 43 . In particular, very high magnitudes of groundwater level changes have been observed in the near-field of large earthquakes 40 , 41 , that can overpass by far the magnitudes of groundwater variations created by monsoons 42 . Despite a high variability of the magnitudes of groundwater level changes caused by earthquakes, many observations show a characteristic shape of transient groundwater level changes in the near and intermediate fields of large earthquakes, with an abrupt increase, followed by a slow decay of the water level over a few months 18 .…”

“…Despite a high variability of the magnitudes of groundwater level changes caused by earthquakes, many observations show a characteristic shape of transient groundwater level changes in the near and intermediate fields of large earthquakes, with an abrupt increase, followed by a slow decay of the water level over a few months 18 . In the near-field of earthquakes, the stream-flow discharge reaches a peak with a time-delay of up to several days 42 , 44 in down-rivers or valleys, as a result of released groundwaters from consolidation of sediments or permeability increases 16 , and water diffusion in river catchments from elevated areas to lower areas 16 . Due to the strong similarities between the time-series of co-seismic groundwater changes in the near-field and the time-dependent shape of the landslide kinematics (and particularly the delay observed in our data), we conjecture that the landslide kinematics observed here has a similar origin.…”

Stronger Peak Ground Motion, Beyond the Threshold to Initiate a Response, Does Not Lead to Larger Stream Discharge Responses to Earthquakes

“…Following earthquakes, it has long been noted that the amount of water discharged at Earth's surface can increase (e.g., Pliny,the Elder,. The magnitude can be substantial, >1 km 3 of excess water in streams (Mohr et al, 2017), and elevated discharge can persist for months (e.g., Liu et al, 2017;Muir-Wood & King, 1993;Rojstaczer et al, 1995). Even dry streams may begin to flow or streams or ponds may disappear (Curci & Tertulliani, 2015).…”

Hydrological, Geochemical and Geophysical Changes Related to Earthquakes and Slow-Slip Events: Introduction

“…Liu et al (2017) report streamflow changes at 23 gauges in central Taiwan after the 1999 M W 7.6 Chi-Chi earthquake. Post-earthquake increases were recorded at 22 gauges and are attributed to rock fracturing by seismic shaking as well as pore pressure rise due to compressive strain.…”