TY - JOUR
T1 - Hydrochemical monitoring, petrological observation, and geochemical modeling of fault healing after an earthquake
AU - Wästeby, Niklas
AU - Skelton, Alasdair
AU - Tollefsen, Elin
AU - Andrén, Margareta
AU - Stockmann, Gabrielle
AU - Claesson Liljedahl, Lillemor
AU - Sturkell, Erik
AU - Mörth, Magnus
PY - 2014/7
Y1 - 2014/7
N2 - Based on hydrochemical monitoring, petrological observations, and geochemical modeling, we identify a mechanism and estimate a time scale for fault healing after an earthquake. Hydrochemical monitoring of groundwater samples from an aquifer, which is at an approximate depth of 1200m, was conducted over a period of 10years. Groundwater samples have been taken from a borehole (HU-01) that crosses the Húsavík-Flatey Fault (HFF) near Húsavík town, northern Iceland. After 10weeks of sampling, on 16 September 2002, an M 5.8 earthquake occurred on the Grimsey Lineament, which is approximately parallel to the HFF. This earthquake caused rupturing of a hydrological barrier resulting in an influx of groundwater from a second aquifer, which was recorded by 15-20% concentration increases for some cations and anions. This was followed by hydrochemical recovery. Based on petrological observations of tectonically exhumed fault rocks, we conclude that hydrochemical recovery recorded fault healing by precipitation of secondary minerals along fractures. Because hydrochemical recovery accelerated with time, we conclude that the growth rate of these minerals was controlled by reaction rates at mineral-water interfaces. Geochemical modeling confirmed that the secondary minerals which formed along fractures were saturated in the sampled groundwater. Fault healing and therefore hydrochemical recovery was periodically interrupted by refracturing events. Supported by field and petrographic evidence, we conclude that these events were caused by changes of fluid pressure probably coupled with earthquakes. These events became successively smaller as groundwater flux decreased with time. Despite refracturing, hydrochemical recovery reached completion 8-10years after the earthquake. Key Points Hydrochemical monitoring records fault healing after an earthquake Mineral growth along fractures is surface controlled The time scale of fault healing is 8-10years
AB - Based on hydrochemical monitoring, petrological observations, and geochemical modeling, we identify a mechanism and estimate a time scale for fault healing after an earthquake. Hydrochemical monitoring of groundwater samples from an aquifer, which is at an approximate depth of 1200m, was conducted over a period of 10years. Groundwater samples have been taken from a borehole (HU-01) that crosses the Húsavík-Flatey Fault (HFF) near Húsavík town, northern Iceland. After 10weeks of sampling, on 16 September 2002, an M 5.8 earthquake occurred on the Grimsey Lineament, which is approximately parallel to the HFF. This earthquake caused rupturing of a hydrological barrier resulting in an influx of groundwater from a second aquifer, which was recorded by 15-20% concentration increases for some cations and anions. This was followed by hydrochemical recovery. Based on petrological observations of tectonically exhumed fault rocks, we conclude that hydrochemical recovery recorded fault healing by precipitation of secondary minerals along fractures. Because hydrochemical recovery accelerated with time, we conclude that the growth rate of these minerals was controlled by reaction rates at mineral-water interfaces. Geochemical modeling confirmed that the secondary minerals which formed along fractures were saturated in the sampled groundwater. Fault healing and therefore hydrochemical recovery was periodically interrupted by refracturing events. Supported by field and petrographic evidence, we conclude that these events were caused by changes of fluid pressure probably coupled with earthquakes. These events became successively smaller as groundwater flux decreased with time. Despite refracturing, hydrochemical recovery reached completion 8-10years after the earthquake. Key Points Hydrochemical monitoring records fault healing after an earthquake Mineral growth along fractures is surface controlled The time scale of fault healing is 8-10years
KW - fault healing
KW - geochemical modeling
KW - hydrochemical monitoring
KW - mineral growth
KW - petrological studies
UR - http://www.scopus.com/inward/record.url?scp=84906081523&partnerID=8YFLogxK
U2 - 10.1002/2013JB010715
DO - 10.1002/2013JB010715
M3 - Article
AN - SCOPUS:84906081523
SN - 2169-9313
VL - 119
SP - 5727
EP - 5740
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
IS - 7
ER -