GNGTS 2013 - Atti del 32° Convegno Nazionale

faults, Shamir (2006) thinks that they extend northeastward and produce subsided, fault-bounded depocentres within the Dead Sea basin. More studies and, possibly, also the use of some seismograms of the time are needed, however, before we can confirm our very prelimary results of a dip-slip source NNE oriented in 1927 (see Tab. 2 and Fig. 2). The hypothesis of the Dead Sea as a pull-apart basin had been proposed by Garfunkel et al. (1981). We comment on, that such a basin, or a rhomboidal-shaped basin, needs bordering normal faults also north and south of the depression. In Fig. 1, we reproduce the interpretative fault map of the active late phase structure of the Dead Sea Depression by Shamir (2006; his Fig. n. 9). He used blue lines for previously mapped faults (we refer to his original caption for the fault references) and in black the newly mapped faults based on seismicity (Shamir, 2006) and seismic data of other authors (we refer again to the original caption of the figure). The intensity data used. We treated the 133 point intensities, I , provided by Avni (1999; and written communication, 2013). Following our procedure, which applies the Chauvenet method (Pettenati and Sirovich, 2007), we looked for statistical outliers. We found that, in this case, the epicentral location was crucial; thus, with a Dead Sea epicentre there were some outliers of high intensities to the north (Yarmuch-Fall I =8.5; Reyneh I =8), whilst an epicentre more Nward produced few outliers with low intensitiy to the south. In this preliminary experiment, we used the whole dataset, which is shown in Fig. 2A using the natural-neighbor n-n contour algorithm (Sirovich et al. , 2002); there are four points of degree 9. Remember that the n-n isoseismals strictly honour the data. You can see the dots corresponding to Yarmuch-Fall and Reyneh in the small brownish island of degree VIII in the upper part of Fig. 2A. We treated half-degrees as real numbers. Fig. 1 – Tectonic interpretation of the Dead Sea region by Shamir (2006; his Fig. n. 9). Fig. 2 – A: point intensities of the 1927 earthquake by Avni (1999) contoured with the n-n algorithm (see text); B: synthetic intensities produced by our inverted source of Tab. 2; the only point of degree 9 is marked by an arrow. 126 GNGTS 2013 S essione 1.1