May 21, 2003 Tsunami: N. Algeria

About 40 to 80 cm of uplift of the sea floor was measured along the coast of Algeria between Reghaia and Zemmouri elBahri. A tsunami with a maximum estimated wave height of 2 m caused damage to boats in the Balearic Islands, Spain, especially in Puerto de Mahon, where 10 boats sank. It was recorded on tide gauges at Palma de Mallorca, Spain; Nice, France; and Genoa, Italy. The tsunami was also observed on the coast of Alicante, Castellon and Murcia, Spain. (reference #1053)

Observed tsunami waves of up to 3-m height with a mean period of 10-12 minutes were reported on the southeastern coast of Majorca and Menorca, and in Ibiza in the Spanish Balearic Islands located about 250 km north of the epicentral region. The waves caused significant damage to hundreds of vessels in harbors and ports. On the Algerian coast in the epicentral region, eyewitness accounts report a 100-m recession of the sea in coastal sections of Algiers and Boumerdes, and fishermen in the port of Zemmouri-El-Bahri, reported a drop in water depth to less than 1 m with several boats ending up resting on the sea bottom before the water returned. Underwater telephone cables were severed by the earthquake and/or tsunami cutting communications between Europe and Asia, the Middle East, and the Pacific. (reference #3025)

The destructive Zemmouri earthquake of 2003 May 21 (Mw 6.8) occurred at 18:44 (GMT) along the coast, 50 km east of the city of Algiers, between the cities of Zemmouri and Boumerdès. This shock, the largest felt in this region since the 1716 event, had the epicenter located very close to the coast (about 4 km) and the earthquake produced severe damage and more than 2,000 victims. Two main phenomena were associated to the earthquake: shoreline uplift along 50 km and a tsunami, triggered either by the earthquake itself or by a submarine landslide. According to Dr. Yelles, director of the CRAAG center in Algiers, the tsunami waves were generated by a river sediment slide. In fact, the area is well known for a large sediment deposited by a river, a deposit which is highly unstable. Instantaneously with the Zemmouri earthquake, a tsunami was generated along the northern Algerian coasts. No run-up values were reported along the Algerian coasts, indicating that the tsunami waves, if any, were not high enough to inundate beyond original shoreline. (reference #4139)

A 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 (MW 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. (reference #12057)

The earthquake generated a tsunami observed as far away as the southern coast of Spain, but little or no damage was done locally. (reference #13026)

More than 150 boats sunk or damaged [Balearic Islands] (reference #11164, v.2)