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Documentation and Monitoring of Active Structures at El Hierro: Potential of Flank Collapse from the Present Seismo-volcanic Crisis and Eruption

Project: Research

Description

After four months of low magnitude seismic activity and continuous deformation, the Island of El Hierro in the Canarian Achipelago erupted on 10 October 2011. Since that date, seismic activity has been slowly increasing in magnitude, with more than 34 Ml>3 earthquakes (four of which have Ml> 4) occurring since 1 November. The largest, a Ml 4.6, intensity (EMS) IV-V earthquake occurred on the 11/11/11 and was felt across El Hierro as well as in the neighbouring Tenerife and La Palma Islands. The current eruption has also extended, with activity now taking place from several vents describing an approximate north-south alignment a short distance offshore. Most ominously this alignment parallels a prominent band of young cinder cones and possible rifting that extends northwards across the island and this area has now been placed on red alert status. Moreover, this alignment parallels the pattern of present seismicity that bisects the island, as well as apparently structurally controlled segments of the cliffed coastline. El Hierro, although the smallest island in the Canary group, represents just the uppermost 1500 metres of a very large volcano that extends more than three kilometres below sea level. Its distinctive scalloped coastline is the result of at least four large-scale flank collapses, occurring as recently as 15 thousand years ago, and the current deformation and seismic activity could trigger a new flank collapse or reactivate one of the older collapses. The official Spanish agency (IGN) responsible for monitoring the seismicity also installed 4 GPS stations in mid July 2011 to record variations in distance between these points, while thekey local group for volcanological research (INVOLCAN) focuses mainly on geochemical monitoring (CO2 and radon emissions) but has a further 6 GPS stations, some pre-dating the crisis, which measure absolute movement of the stations, with data processed by personnel from Nagoya University inJapan. These datasets, although valuable, only provide information from scattered points, and do not represent the integrated structural documentation and analysis of recent and potential future overall deformation presently proposed. This structural analysis needs to be carried out urgently, to seize the scientific opportunity to capture baseline data and to provide a volcano-tectonic framework in which to place the monitoring data outlined above. In this way the progression of potential flank instability can be documented and modelled, work that is crucial to understanding this widespread and potentially catastrophic phenomenon, yet presently does not exist.
On 27 October 2011, a meeting took place of the members of the scientific committee set up as a result of the present crisis. This meeting, attended by the PI, confirmed that no group is investigating active fractures and other structures in the field, emphasising the urgency of,
1) establishing this baseline structural framework and,
2) enacting monitoring networks and procedures to record the pattern and rate at which this framework deforms.
We therefore propose in this project a field campaign to map and analyse active volcano-seismo-gravitational structures on the island and to set up a control system that will monitor the evolution of these structures. The work will contribute principally to modelling and understanding the overall deformation of volcanic edifices during eruptions and the generation and evolution of areas of instability. Additionally, the work has the potential to make predictions and warnings useful in the current crisis. Once the initial field campaign is finished, repeat measurements will be performed by personnel from the relevant Spanish agencies, INVOLCAN and ITER. The ultimate aim is to further collaborate with these colleagues in a follow-up multi-disciplinary project proposal.
StatusFinished
Effective start/end date1/12/1130/03/12

Funding

Award relations

Documentation and Monitoring of Active Structures at El Hierro: Potential of Flank Collapse from the Present Seismo-volcanic Crisis and Eruption

Dr Carmen Solana & Dr Derek Rust

Natural Environment Research Council: £21,186.00

1/12/1130/03/12

Award date: 15/12/11

Funding: R: ResearchAward

Relations

ID: 3274579