The tsunami induced by the 2003 Zemmouri earthquake (M_W= 6.9, Algeria): modelling and results

Abstract

S U M M A R YA strong tsunami with sea disturbances observed along the Algerian coast, but with significant damage mainly in the Balearic Islands (Spain) harbours, affected the western Mediterranean following the 2003 Zemmouri earthquake (M W 6.9, Algeria). An average regional uplift of 0.55 m was measured along the shoreline in the epicentral area. Field observations, main shock and aftershocks characteristics are consistent with thrust along a ∼55-km-long rupture, trending NE-SW, dipping SE. The seismotectonic parameters indicate a hypocentre 7-8 km deep and a possible fault break between 5 and 15 km offshore. Several tide gauges located in the western Mediterranean Coast indicated an average of 0.4 m of sea-level change with a maximum of 2 m in the Balearic Islands. We generated high-resolution bathymetry grids from the Algerian coasts to the Balearic Islands coasts in order to test different seismic sources (with different fault rupture location, strike and dip) and model the tsunami initiation and propagation.For the modelling we employed the Crank-Nicolson numerical schema with a finite difference method and the Okada elastic dislocation theory for the fault rupture. We also highlight the different factors responsible for waves' amplification around the Balearic coast. The best fit between synthetic and real data (tide gauges, GPS levelling and coastal uplift as compared to run-up values) are obtained for a thrust rupture comparable with the earthquake fault inferred from seismotectonic studies and located within 15 km offshore. An analysis of T waves reinforces the earthquake rupture origin for the tsunami. This study presents the results and modelling of a major tsunami recorded in the western Mediterranean Sea.

Tsunami hazard at the Western Mediterranean Spanish coast from seismic sources

“…This area absorbs around 2-4 mm/yr (40-60%) of the total convergence between the plates (Morel and Meghraoui, 1996;Meghraoui and Doumaz, 1996;Serpelloni et al, 2007). The mentioned tectonic structures, frequently known as seismogenic inland (Bezzeghoud et al, 1995;Yelles-Chaouche et al, 2003), have their continuation offshore and are the most probable sources of tsunamis in the area (Alasset et al, 2006).…”

Probabilistic tsunami hazard in the Mediterranean Sea

“…and 1748 in the Gulf of Corinth and in 1783 in the Messina strait. The most recent destructive tsunamis occurred in the Aegean Sea in 1956 with runup heights reaching 25 m [Papazachos et al, 1985] and north of Algeria in 2003 with runup heights up to 2 m in the Balearic Islands [Alasset et al, 2006]. Each of these tsunamis was generated by a strong earthquake [Soloviev, 1990;Papadopoulos and Fokaefs, 2005].…”

Calibration of a real-time tsunami detection algorithm for sites with no instrumental tsunami records: application to coastal tide-gauge stations in eastern Sicily, Italy

“…As for the Mediterranean Sea, only in recent years digital tide-gauge stations have been installed with (or upgraded to) a sampling rate adequate to cover tsunami recording needs, and digital records of real tsunamis are very few. The best recorded case is the 23 May 2003 tsunami induced by the Boumerdés-Zemmouri M w = 6.9 earthquake (in Algeria) that was recorded by more than 20 tide-gauge stations in the western and central Mediterranean (see Alasset et al, 2006;Heidarzadeh and Satake, 2013).…”