Origin time 10:35:31 UTC Depth 45 km (28 mi) Max. intensity IV (Largely observed) Date 12 February 2007 | Magnitude 6.1 Mw Type Oblique-slip Peak acceleration .0001321g | |
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Similar 2007 Guatemala earthquake, 2007 Kent earthquake, 2007 Gisborne earthquake, March 2007 Sumatra, 2007 Solomon Islands e | ||
The 2007 Iberian Peninsula earthquake (also known as the 2007 Horseshoe earthquake) occurred at 10:35:31 Greenwich Mean Time on February 12 with its epicentre in the eastern Atlantic Ocean, off the coasts of Portugal and Morocco. The earthquake had a moment magnitude of 6.1 and a maximum intensity of IV (Largely observed) on the European macroseismic scale. The shock occurred at a plate boundary where a number of large, very large, and great earthquakes are known to have taken place as far back as the eighteenth-century. The event was captured by a network of strong motion instruments in Spain, but due to the distance at which the shock was recorded, the peak ground acceleration was very low.
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Tectonic setting
On its west, south, and east sides the African Plate is surrounded by spreading centers, and on the north side, the plate forms a convergent boundary with the Eurasian Plate in the central and eastern Mediterranean Sea. At the extreme northwestern boundary of the plate lies the Azores Triple Junction, where the Mid-Atlantic Ridge meets the right-lateral strike-slip Azores–Gibraltar Transform Fault, which is an east–west trending structure that continues toward the Strait of Gibraltar as the Gloria Fault.
Earthquake
The undersea earthquake occurred about 175 kilometres (109 mi) from the southwest coast of Portugal in the eastern Horseshoe Abyssal Plain, a geological feature that was the same location of the 1969 Portugal earthquake. The shock was widely felt in Portugal, Spain, and Morocco, but did not cause any damage due to its distance from the shore, and was followed by four small aftershocks of M3.5 or less.
Intensity
In Morocco, intensities for the event were up to IV (Largely observed) in the coastal cities of Tangier, Rabat, Casablanca, El Jadida and Safi. Slightly higher intensities were reported in the taller buildings in Casablanca. Intensities were about II (Scarcely felt) in the much more distant cities of Agadir, Ouarzazet, Errachidia, and Taza. Some of these towns were up to 650 kilometres (400 mi) away. The depth of the event was listed as one reason why the shock was felt over such a wide area.
Strong motion
The Instituto Geográfico Nacional operates a network of strong motion instruments in Spain. Eight accelerometers recorded the event at distances between 326–623 kilometres (203–387 mi). The three nearest stations (Cartaya, Huelva, and Matalascañas) were on relatively soft soil and recorded the highest ground motion. The station at Cartaya saw a peak ground acceleration of .0001321g.