Earthquake Report: Mediterranean!

We just had a M 6.1 earthquake and a few aftershocks (M 4-5) in the western Mediterranean,

Here is the USGS website for this earthquake.

Here is a map showing the 5 largest earthquakes as circles.

There is a legend that shows how moment tensors can be interpreted. Moment tensors are graphical solutions of seismic data that show two possible fault plane solutions. One must use local tectonics, along with other data, to be able to interpret which of the two possible solutions is correct. The legend shows how these two solutions are oriented for each example (Normal/Extensional, Thrust/Compressional, and Strike-Slip/Shear). There is more about moment tensors and focal mechanisms at the USGS.


For more on the graphical representation of moment tensors and focal mechnisms, check this IRIS video out:

Based on the mapping presented by Gracia et al (2012), Casciello et al. (2016), and the bathymetry, this earthquake may have ruptured one of the northeast striking structures that are shown in the lower left part of the Gracia et al. (2012) map. Therefore I interpret this earthquake to be a left-lateral strike-slip earthquake.

Here is a close up of Gracia et al. (2012) Figure 1. I provide their caption below in blockquote.


Figure 1. Schematic geological map of the Westernmost Mediterranean highlighting the position of the Alboran Domain enclosed between Iberia and northwest Africa. Its metamorphic rocks compose the floor of the western Alboran Sea and form the inner zones of the Betics and Rif mountain chains.

Here is the Casciello et al (2016) figure showing their tectonic interpretation. Figure is their map and Figure 2 is an earlier tectonic interpretation (Andrieux et al., 1971). I provide their caption below in blockquote.


Fig. 1. Regional topographic and bathymetric map of the southeast Iberian margin constructed from digital grids released by SRTM-3, IEO bathymetry (Ballesteros et al., 2008; Mu˜noz et al., 2008) and MEDIMAP multibeam compilation (MediMap et al., 2008) at  90m grid-size. Epicenters of the largest historical earthquakes (MSK Intensity>VIII) in the region are depicted by a white star (I.G.N., 2010). Grey arrows pointing opposite each other show the direction of convergence between the Eurasian and African plates from NUVEL1 model (DeMets et al., 2010). The black outlined rectangle depicts the study area presented in Fig. 2. BSF: Bajo Segura Fault; AMF: Alhama de Murcia Fault, PF: Palomares Fault, CF: Carboneras Fault, YF: Yusuf Fault, AR: Alboran Ridge. Inset: Plate tectonic setting and main geodynamic domains of the south Iberian margin along the boundary between the Eurasian and African Plates.

Fig. 3. Original model by Andrieux et al. (1971) to explain the formation of the Gibraltar Arc. The Alboran microplate would resist the eastward movement of the European and African plates, which are
forced by oceanic expansion in the Atlantic, causing the formation of the Betic-Rif chains.

Category(s): College Redwoods, earthquake, education, europe, geology, HSU, plate tectonics, strike-slip, Transform

2 Responses in other blogs/articles

  1. […] a moment tensor from an earthquake in the western Mediterranean from 2016.01.24 in the above map. Here is my Earthquake Report for that seismicity and below is the map from that […]

  2. […] a moment tensor from an earthquake in the western Mediterranean from 2016.01.24 in the above map. Here is my Earthquake Report for that seismicity and below is the map from that […]

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