WP 5.2 Mapping and interpretation of earthquake rupture in the Reykjanes peninsula and other surface effects there and in the SISZ

Start date or starting event:

M0

Lead contractor:

NVI

Participants:

NVI, IMOR

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Objectives:

To identify distant faults (on the Reykjanes peninsula) whose movement was triggered by the 17 June, 2000 earthquake in the South Iceland lowland.  To map the extent of surface rupture along these distant faults and other surface effects (rock fall and slope failure) in the entire area of  SISZ and the Reykjanes peninsula.  To characterize the faults along which motion was triggered in order to determine future predictability of minor fault movements.

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Inputs:

·         Existing and evolving seismic data (from the SIL-network) and existing GPS data. 

·         Existing knowledge about faults in the area.

·         Georeferenced aerial photographs and geological maps.

·         Fieldwork, to include mapping with Differential GPS unit.

·         Geographic Information Systems software (Arc/Info, Trimble Pathfinder, Erdas Imagine).

Methodology / work description:

Within minutes of the  M=6.6 earthquake in South Iceland on  June 17, 2000, smaller earthquakes occurred along a 100 km length of the plate boundary to the west of the main shock. The entire length of the Reykjanes peninsula was affected. The largest was a 4.8 Mw shock 85 km west of the mainshock. Rock fall was observed and reported over a wide area in the central part of Reykjanes peninsula, and surface rupture has been observed in several places. Most of the small earthquakes occurred at shallow depths (< 5 km) along pre-existing faults. At least two faults in the Krýsuvík area experienced significant movement, while many others show evidence of minor movement or shaking. Interferometry has shown that a fault centered under Lake Kleifarvatn has experienced as much as 1 m of aseismic slip and is the probably cause of water draining out of the lake at the rate of 9 mm per day. Slope failure and large rock fall has occurred along many steep scarps in the vicinity of Lake Kleifarvatn. GIS has been used to identify areas where clusters of small earthquakes (M < 2) or single events (M=2) have occurred along the strike of pre-existing faults. Some fieldwork has been conducted in those areas to determine the surface manifestations of the seismicity. This part of Reykjanes peninsula is in close proximity to the greater Reykjavík area, including Hafnarfjördur and the nearby Straumsvík aluminum smelting facility. The area of highest seismicity is being newly exploited for geothermal energy and increasing numbers of summer homes are being built there. Criteria will be developed to evaluate the degree of potential hazard to the various users of the area.  Additional fieldwork is required to cover the areas affected by small, shallow earthquakes and to map in detail areas of ground rupture, rock fall and slope failure.  Results from detailed field mapping will be integrated with geophysical data using GIS software to develop a hazard map for Reykjanes peninsula. These data will also provide a test for dynamic models of Coulomb stress change resulting from earthquakes in the South Iceland lowland.

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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 milestone date indicated.