Seismic hazard assessment accounting for earthquake-induced phenomena
through spatial multi-criteria analysis in Xerias torrent basin, Greece
The present study focuses on the area of the Xerias torrent drainage basin, located at
Northeastern Peloponnese, Greece. The study area is situated at the eastern part of the Gulf of
Corinth, an active tectonic rift, characterized by high seismic activity and intense extension
which is accommodated by a series of major active normal faults. As a result, it has frequently
suffered damage from earthquakes which in some cases were accompanied by seismically-
induced phenomena. These secondary phenomena include landslides and soil liquefaction and
in some cases have the potential to cause more damage and casualties than the earthquake
itself. Classic deterministic and probabilistic approaches of seismic hazard assessment do not
account for seismically-induced phenomena and accordingly such analyses overlook locations
prone to these secondary effects. The aim of our research is to evaluate seismic hazard not
only as the hazard associated with the occurrence of potential earthquakes in the particular
area, but also assess areas exposed to slope destabilization phenomena and soil liquefaction
under seismic shaking. For this purpose we will use the pure statistical and the semi-statistical
seismic hazard approaches along with the Analytic Hierarchy Process (AHP) to estimate the
susceptibility of the study area to earthquakes and their triggering effects. AHP is a multi-
criteria decision making method that helps to deal with a complex problem taking into
account multiple conflicting criteria. The extent of the study area is limited, so classic
probabilistic seismic hazard assessment yields a uniform seismic hazard throughout the study
area. Afterwards, we evaluated separately the hazard from seismically-induced landslides and
soil liquefaction and subsequently we stacked them into one single hazard map reflecting the
hazard due to seismically-induced phenomena. Such map complement the standard PSHA
maps and highlight areas that need special attention by planners and authorities so as to
mitigate not only the consequences of earthquakes but also their secondary effects.
Figure 1. The digital elevation model (DEM) of the Xerias drainage basin superimposed by
the Xerias torrent, the main towns and the. The red rectangle in the inset highlights the
location of the study area within the Greek territory.
Figure 2. Map of the study area showing local active and probable active faults (E.P.P.O.
Neotektonic map “Korinthos” sheet 1:100.000) along with the epicenters of historical and
instrumentally recorded major earthquakes (Ms>6.0) (Ambraseys & Jackson 1990, 1997;
Papazachos & Papazachou 2003).
Calculate the Hazard of the study
area
Hazard 1 earthquake
triggered landslide
Slope
0-5
5-12
12-18
18-25
25-35
>35
Geology
Recent deposits
Neogene formations
Shales-chert formation
Carbonate rocks
Arias intensity
Spi20
Flat slope
Lower slope
Valley
Middle slope
Upper slope
Ridge
Distance to fault (m)
0-50
50-100
100-150
150-200
>200
Distance to road (m)
0-50
50-100
100-150
150-200
>200
Distance to stream (m)
0-50
50-100
100-150
150-200
>200
Aspect
Flat
North
NE
East
SE
South
SW
West
NW
Land use
Burnt area
Mine
Agricultural Land
Bush
Forest
Urban
AHP
Hazard 2 earthquake
triggered liquefaction
Soil (age)
Late Holocene
Holocen
Pleistocene
Pre-Pleistocen
cti/twi
0-4
4-6
6-8
8-10
>10
PGAm
0,05
Distance to stream (m)
0-50
50-100
100-150
150-200
>200
Vs30
D
C
B
AHP
Stacking
Goal
Subgoal
Factors
Categories
Figure 3. Workflow of the adopted approach for the hazard assessment of earthquake-induced phenomena
Figure 4. Thematic layers of the causative factors that contribute to the likelihood of
earthquake-induced landslides. a) Land use, b) slope aspect, c) distance to streams, d) distance
to roads, e) distance to faults, f) slope position, g) Arias Intensity, h) lithology, and i) slope
angle.
Figure 5. Thematic layers of the causative factors that contribute to the likelihood of soil
liquefaction. a) Age of liquefable soils, b) compound topographic index, c) magnitude
weighted PGA, d) distance to streams, and e) site class.
Figure 6. Earthquake-induced landslide hazard zonation map. a) Mean, b) minimum and c)
maximum estimates.
Figure 7. Liquefaction hazard zonation map. a) Minimum, b) Mean and c) Maximum
estimates.
Figure 8. Hazard zonation map for earthquake-induced phenomena. a) Minimum, b) Mean
and c) Maximum estimates.