Assessment of potential seismic hazard for sensitive facilities 1 by applying seismo-tectonic criteria : an example from the 2 Levant region

11 We present a methodology for mapping faults that constitute a potential hazard to 12 structures, with an emphasis on special facilities such as dams and nuclear power plants. 13 The methodology categorises faults by hierarchical seismo-tectonic criteria, which are 14 designed according to the degree of certainty for recent activity and the accessibility of 15 the information within a given region. First, the instrumental seismicity is statistically 16 processed to obtain the gridded seismicity of the earthquake density and the seismic 17 moment density parameters. Their spatial distribution reveals the zones of the seismic 18 sources, within the examined period. We combine these results with geodetic slip rates, 19 historical earthquake data, geological maps and other sources to define and categorise 20 faults that are likely to generate significant earthquakes (M ≥ 6.0). Their mapping is 21 fundamental for seismo-tectonic modelling and for PSHA analyses. In addition, for 22 surface rupture hazard, we create a database and a map of capable faults, by developing 23 criteria according to the regional stratigraphy and the seismotectonic configuration. The 24 relationship between seismicity slip dynamics and fault activity through time is an 25 intrinsic result of our analysis that allows revealing the tectonic evolution of a given 26 region. The presented methodology expands the ability to differentiate between 27 subgroups for planning or maintenance of different constructions or for research aims, 28 and can be applied in other regions. 29 Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2019-67 Manuscript under review for journal Nat. Hazards Earth Syst. Sci. Discussion started: 2 May 2019 c © Author(s) 2019. CC BY 4.0 License.


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The establishment of sensitive facilities such as nuclear power plants or dams have 31 been raising the seismic risk to higher levels and entail the need for a profound 32 understanding of the seismic hazard (e.g. Marano et al., 2010). Probably the most famous 33 example is the destruction of the Fukushima nuclear power plant by tsunami waves 34 caused by the 2011 M w = 9.0 Tohoku-oki earthquake, which has been affecting an 35 extensive region ever since. Identifying and characterising the regional seismic sources 36 and their potential hazard is therefore fundamental for siting and designing of potential 37 facilities, and for risk management. Additionally, in the case of infrastructures, the hazard 38 also includes surface rupture in close proximity to the construction. The goals of this 39 study are to define the regional main seismic sources, presuming that these are the  generating the Suez rift and the DST which separate the Sinai sub-plate from the African 89 and the Arab plates (Fig. 1). The Suez rift, however, has shown relatively minor signs of 90 deformation since the end of the Miocene (Garfunkel and Bartov, 1977; Joffe and 91 Garfunkel, 1987;Steckler et al., 1988), while the DST system remains the most active 92 tectonic feature in the area. In the Easternmost Mediterranean, the current plate boundary 93 deformation is taking place along the convergent Cyprian Arc (Fig. 1), where the 94 Anatolian plate overrides the plates of Africa and Sinai (e.g., Mckenzie, 1970). 95 The 1000-km DST is the largest fault system in the east-Mediterranean region ( Fig.   96 1). Its northern section crosses northwest Syria in a N-S orientation; several recent large 97 earthquakes were attributed to this section during the past two millennia (Meghraoui et 98 al., 2003). The middle section of the DST is a restraining bend (LRB; Fig. 1), 99 characterised by transpression deformation (Quennell, 1959). The section is branched to a 100 few segments that transfer the main component of the strike-slip motion in Lebanon area 101 (Gomez et al., 2003;2007). The Israel region is located along the southern section of the 102 DST but seismically it is also affected by the activity of the middle part. 103 The southern part of the DST (Fig. 1) is dominated by a sinistral motion of 104 approximately ~5 mm/yr, summing up to ~105-km of left-lateral displacement over a 105 period of 15-20 million years (e.g. Garfunkel, 1981;2014). It is marked by a pronounced  where the southern part is assumed to be relatively rigid, while northward, normal faults 129 orientated E-W generate N-S extension expressed by graben and horst structures (Ron 130 and Eyal, 1985).  Table A1).

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The establishment of Quaternary formation database (Table A2) (Table A3). The latter are limited to the extensions of mapped faults that are within 157 Israel, and/or the main DST segments. The criteria for selecting these faults are discussed 158 in section 6. 159 160 4. Seismological analysis 161 We analyse the spatial distribution of seismic events in order to reveal the regional 162 seismic pattern, which helps to define the main seismic sources and develop an 163 independent criterion for Quaternary active faults. In order to define the seismicity-based 164 criterion, we designe seismic criteria that are based on the distribution of two parameters:  new catalogue with more precise locations of hypocentres (Wetzler and Kurzon 2016).

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As part of the relocation process, ~900 earthquakes were excluded for various reasons,   In order to assess the applicability of the following seismic processing and analysis, 187 we define the network coverage area as the zone in which the hypocentres are relatively  In order to quantitatively characterise the regional seismicity and associate the 194 earthquakes with mapped faults we examine two parameters: a) earthquake kernel 195 density and b) seismic moment ( 0 ) kernel density. Both parameters are obtained through 196 the following spatial data processing. A regional scan is carried out in a 0.5-km interval  The 6-km radius from each grid-point, and the Gaussian function and its standard  The earthquake kernel density parameter, , is calculated by counting all the 211 weighted events within a 6-km radius from each grid point, dividing their sum by the 212 sampler area (πr 2 ) and normalising by the duration of the earthquake catalogue: where N is the total number of events within the radius r, d(n) is the distance between an 215 event n and the circle centre; is the standard deviation of the Gaussian function, and T 216 is the duration of the earthquake catalogue. Units are [

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The 0 kernel density parameter, where N is the total number of events within the radius r, 0 ( ) is the seismic moment  This contrast is predominant in the Sea of Galilee, which contains high earthquake kernel 275 density ( Fig. 3) but is less significant in the seismic moment kernel density (Fig. 4).  (Table 6).  Large earthquakes along the Cyprian Arc (Fig. 1) can also generate tsunamis that 341 might affect the coastline of Israel (Salamon et al., 2000). This source is not analysed and 342 mapped here, but should be taken into account in regional seismotectonic models.  we assume that faults that were active during the present regional stress regime (Zoback,364 1992) are more likely to activate in the near future. The regional stress state within the  Finally, in regions where Quaternary cover is absent, we utilise a seismological 375 criterion (Fig. 6) 1. Main strike-slip faults of the DST: identified here as main sources for large regional 382 earthquakes (Fig. 7).  (Table A2) to rupture the earth's surface at least once since the 386 Quaternary. This criterion is mainly related to zones covered by Quaternary units.  Fig. 6). Therefore, the overlap area (Fig. 6)    while the hazard is perceptible, the seismic data is sparse comparing to very active zones.

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Taking into the account that the earthquake phenomenon is a stochastic process and its 435 predictability is limited, we develop a methodology that takes advantage of incorporating 436 interdisciplinary information with statistical analyses for seismic hazard evaluation. We by analysing recorded seismicity and applying statistic-based data processing (Figs. 3, 4).

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However, instrumental seismological data is practically limited, and the precision of the 440 results depends on the amount and the quality of the data, regardless of the specific 441 statistical method. This gap is closed by geodetic measurements, paleo-seismology and 442 historical information.

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Throughout the capable fault map (Fig. 7), the information about the seismic intervals Sinai-Negev shear belt (Bartov, 1974)). Further research of these zones is required for 473 better understanding the local variation of the seismic patterns.  2. The regional main seismic sources are primarily defined by the recent slip rates.

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Geologic and geodetic slip rates, as well as long historical record and high-resolution 484 mapping enable reliable definition of faults that are likely to generate large earthquakes.

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All the main seismic sources in the Israel region (Fig. 5) are related to the DST activity.  success of this selection is further reinforced by the match between the geological-499 categorised faults and the seismicity criterion (Fig. A3).                        1:50,000 sheets (as of 2018)