Hydrothermal response to a volcano‐tectonic earthquake swarm, Lassen, California

Liao

Water Resources Research

et al. 2016

Hydrologic responses to earthquakes and their mechanisms have been widely studied. Some responses have been attributed to increases in the vertical permeability. However, basic questions remain: How do increases in the vertical permeability occur? How frequently do they occur? Is there a quantitative measure for detecting the occurrence of aquitard breaching? We try to answer these questions by examining data from a dense network of ∼50 monitoring stations of clustered wells in a sedimentary basin near the epicenter of the 1999 M7.6 Chi‐Chi earthquake in western Taiwan. While most stations show evidence that confined aquifers remained confined after the earthquake, about 10% of the stations show evidence of coseismic breaching of aquitards, creating vertical permeability as high as that of aquifers. The water levels in wells without evidence of coseismic breaching of aquitards show tidal responses similar to that of a confined aquifer before and after the earthquake. Those wells with evidence of coseismic breaching of aquitards, on the other hand, show distinctly different postseismic tidal response. Furthermore, the postseismic tidal response of different aquifers became strikingly similar, suggesting that the aquifers became hydraulically connected and the connection was maintained many months thereafter. Breaching of aquitards by large earthquakes has significant implications for a number of societal issues such as the safety of water resources, the security of underground waste repositories, and the production of oil and gas. The method demonstrated here may be used for detecting the occurrence of aquitard breaching by large earthquakes in other seismically active areas.

Section: Previous Studiesmentioning

confidence: 99%

Large earthquakes create vertical permeability by breaching aquitards

Liao

Water Resources Research

et al. 2016

“…These observations have suggested that earthquakes dynamically affect permeability of the Earth’s crust 20 , 21 . Carbon dioxide (CO 2 ) emissions were observed in association with seismicity in the case of the Matsushiro swarm 9 in Japan or, recently, at the Lassen volcano 22 (Cascades Range, USA) and in the Eger Rift 23 (Czech Republic), which suggests connection between the mid-crust and the ground surface through gas transport. However, such examples so far were only observed in the presence of magmatic activity.…”

Section: Introductionmentioning

confidence: 99%

Persistent CO2 emissions and hydrothermal unrest following the 2015 earthquake in Nepal

Girault

Adhikari²,

France‐Lanord

et al. 2018

Nat Commun

Fluid–earthquake interplay, as evidenced by aftershock distributions or earthquake-induced effects on near-surface aquifers, has suggested that earthquakes dynamically affect permeability of the Earth’s crust. The connection between the mid-crust and the surface was further supported by instances of carbon dioxide (CO2) emissions associated with seismic activity, so far only observed in magmatic context. Here we report spectacular non-volcanic CO2 emissions and hydrothermal disturbances at the front of the Nepal Himalayas following the deadly 25 April 2015 Gorkha earthquake (moment magnitude Mw = 7.8). The data show unambiguously the appearance, after the earthquake, sometimes with a delay of several months, of CO2 emissions at several sites separated by > 10 kilometres, associated with persistent changes in hydrothermal discharges, including a complete cessation. These observations reveal that Himalayan hydrothermal systems are sensitive to co- and post- seismic deformation, leading to non-stationary release of metamorphic CO2 from active orogens. Possible pre-seismic effects need further confirmation.

“…There are examples where ground deformation due to mass discharge or the subsurface migration of hot fluids has been detected at volcanichydrothermal systems that can cause phreatic eruptions (e.g., Nakaboh et al 2003;Maeda et al 2017;Doke et al 2018;Miller et al 2018;Kobayashi et al 2018). A number of authors have also discussed the behavior of volcanichydrothermal systems during non-eruptive unrest events using ground deformation data, gravity changes, geomagnetic changes, and heat flux changes (e.g., Fournier and Chardot 2012;Ingebritsen et al 2015;Currenti et al 2017;Tanaka et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Shallow hydrothermal reservoir inferred from post-eruptive deflation at Ontake Volcano as revealed by PALSAR-2 InSAR

Narita

Murakami

2018

Earth Planets Space

In 2014, a phreatic eruption occurred at the Ontake Volcano in Central Japan causing multiple deaths and missing persons. Interferometric Synthetic Aperture Radar data showed local-scale subsidence around the newly created eruptive vents after the eruption. Source modeling resulted in a nearly spherical deflation source emplaced at a depth of 500 m below the vents reflecting post-eruptive depressurization in a shallow hydrothermal reservoir. The cumulative deflation volume reached 7 × 10 5 m 3 3 years after the eruption. Comparison between our source model and GNSS data indicates that this shallow reservoir could have formed by 2007 and remained stable until the 2014 eruption. The absence of significant syn-eruptive subsidence indicates that the shallow reservoir was not the main water source driving the phreatic eruption. Under simple assumptions, mass balance between the shallow reservoir and the discharge plume from the vents indicates most of the water contained in the plume comes from greater depth than the shallow reservoir. To constrain the post-eruptive process, it is necessary to track not only deformation but also plume discharge for 3 years after the eruption.