Geobulletin alpha

News from the Geoblogosphere feed

by Stratigraphy.net
New from Snet: Lithologs, a new tool to create lithological/sedimentological logs online..

Blog post recommendation

Mysterious Spanish Earthquake

Here is what USGS wrote about the M6.3 earthquake Monday, April 12, 2010 at 12:08:10 AM at epicentre (Location 37.078°N, 3.470°W = 25 km SE of Granada, Depth 616.7 km.

“The seismotectonics of the April 11, 2010 M6.3 Spanish earthquake is enigmatic, but the occurrence of deep earthquakes beneath this region of Spain are well-documented. The location of the April 11, 2010 M6.3 and it's unusual depth of 616 km suggests that it is related to the well-studied M7.1 deep Spanish earthquake of March 24, 1954. The epicenter of the 1954 earthquake, based on the distribution of ground shaking at the surface (macroseismicity) and limited instrumental recordings of the earthquake, is beneath the town of Dúrcal, 20 km south of Granada. Since the 1954 earthquake, a handful of small magnitude earthquakes (3 and smaller) have occurred in approximately the same location (Buforn et al., 1991). Southwest of the April 11, 2010 M6.3 earthquake in the area of the Alboran Sea, convergences of the African and Eurasian plates does produce a well-defined zone of small magnitude (M < 4) to depth of 200 km. Other than the localized zone of seismicity near 600 km depth, there are no known earthquakes between 200 km and 600 km depth.“



As far back as 1968 (Isacks et al. in J. Geophys. Res. 73: 5855-5899) explained the 1954 quake as an event occurring in a detached piece of the lithosphere which had been pulled away from its upper portion as a result of a large density contrast between the sinking part of the lithosphere and the surrounding mantle.

There was also a similar deep earthquake under South Spain on 8 March 1990.

Earthquakes like this are too deep to cause ay damage.





Stratigraphy.net | Impressum
Ads: