WP 5.5 Hydrological changes associated with the June 2000 earthquakes

Start date or starting event:

M0

Lead contractor:

UIB

Participants:                                                UIB, UPMC, DF.UNIBO

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Objectives:

1) To explain the observed drastic changes in the ground water and geothermal water  systems and correlate these changes with the June 2000 earthquakes.  2) To contribute to forecasting future large earthquakes in the SISZ through modelling  and 3) predicting preseismic hydraulic changes in the upstream and downstream parts of  an eventual fault plane.

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Inputs:

1) Data on changes in geothermal and groundwater systems in South Iceland in relation to the  June 2000 earthquakes from subcontractor in Iceland. 2) From the same subcontractor televiewer measurements and analysis of the boreholes which now are used for the continuous monitoring of  hydrological changes in the SISZ. 3) Earthquake distribution just prior to and following the June 2000 earthquakes, from IMOR to understand the coupling between fluid flow and seismicity, particularly the aftershock  distribution.  4)  Field observations (from various places) and numerical models of propagation and arrest of  hydrofractures in layered, jointed and faulted rock masses with various mechanical properties.

Methodology / work description:

1) Boundary element, finite element and finite difference programs will be used to model the flow of  overpressured fluids through the layered, jointed and faulted crust of the SISZ and  permeability changes prior to and following the June earthquakes. A preliminary study for a  homogeneous and isotropic crust indicates that the drastic water-level changes in geothermal  drillholes can be broadly related to permeability changes in the upstream and downstream  regions of the earthquake ruptures.  2) Preseismic flow of fluids to, and accumulation on, the eventual rupture zones will be  modelled using standard hydrogeological programs and the numerical programs for modelling fluid flow in fractures.  3) The same programs will be applied to model the postseismic flow of fluids to the tipline  of the mainshock fault planes.  4) Preliminary models  indicate that when the trend of an active  fault coincides with that of the local hydraulic gradient, the yield of springs and wells in  the upstream part decreases but increases in the downstream part. This model will be  developed so as to help forecast future large earthquakes in the SISZ, i.e. to try to detect possible preseismic changes by observing  hydrological changes. 5) The results of the models and measurements will be used to explain the hydrological changes  associated with the June 2000 earthquakes.

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Deliverables including cost of deliverable as percentage of total cost of the proposed project:

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Milestones: Delivery of the above items at the date indicated.