Holocene extreme wave event in Cope Basin, Spain, Western Mediterranean

Lario, Javier; Spencer, Chris; Bardaji, Teresa; Marchante, Angel

Abstract

The Iberian Mediterranean coast has very few geological records of EWE (Extreme Wave Events) such as tsunamis or storm surges. Some historical tsunamis have been reported in the region, however, their impact at the coast has been negligible. In Cope Basin (Murcia) there is a boulder ridge containing boulders of >1 m extending up to 8 masl, which was generated by a EWE, either a tsunami or storm surge. The area's regional geodynamics are governed by the indentation process of the Aguilas Arc that gave place to a major left lateral transcurrent zone, known as the Eastern Betics Shear Zone (EBSZ). Stronger seismic activity in the area is clearly concentrated along faults within the EBSZ which are oriented perpendicular or oblique to the main stress field.
These ENE-WSW to E-W faults have produced instrumental earthquakes of 5.2 Mw and historical ones with an estimated magnitude of 6.2 to 6.9 Mw, although very low instrumental seismic activity has been recorded within the proper Aguilas Arc (Bardají et al., 2015).
Different approaches to calculate the minimum height of the tsunami wave or storm wave capable of moving these boulders have been applied using formulas for a JBB scenario by Engel and May (2012) and for a submerged scenario (Nott, 2003). These models show that storms in this part of the Mediterranean cannot generate these boulder ridges, whereas the decision matrix for tsunamis on the Spanish Mediterranean coast indicates that a 6.0-6.5 Mw earthquake less than 40 km offshore and at a depth of less than 100 km would have the potential to generate a locally destructive tsunami (IOC, 2011). Tsunami generation models also show that in the Iberian Peninsula, Murcia is the province affected by the greatest tsunamis, mainly generated in Northern Algeria (Alvarez-Gómez et al., 2011).

• Presentation Conference Type: Conference Paper (unpublished)
• Conference Name: 5th International Tsunami Field Symposium
• Start Date: Sep 3, 2017
• End Date: Sep 7, 2017
• Acceptance Date: Aug 1, 2017
• Publication Date: Jan 1, 2017
• Deposit Date: Nov 21, 2017
• Peer Reviewed: Peer Reviewed
• Pages: 74-75
• Keywords: EWE, boulder ridge, transport models, tsunami, Murcia
• Public URL: https://uwe-repository.worktribe.com/output/902566
• Publisher URL: http://itfs.campus.ciencias.ulisboa.pt/
• Additional Information: Title of Conference or Conference Proceedings : The 5th International Tsunami Field Symposium
• Contract Date: Nov 21, 2017