The devastating 06.02.2023 Turkey – Syria earthquake of extreme intensity XI: Aposteriori estimates and damage prevention

Abstract

The recent devastating earthquake of Mw7.8 occurred on February 6, 20223 in the Kahramanmaraş region having extreme intensity (XI) on the modified Mercalli scale (MMS) caused the death of more than 52,800 people in Turkey and Syria, as well as severe damages to the infrastructure. The appearance of an unusually strong delta-like S-wave pulse in the seismogram of the main shock and its consequences are analysed, and possible measures to mitigate the possible future high intensity earthquakes are discussed.

Full text

The devastating 06.02.2023 Turkey – Syria
earthquake of extreme intensity XI: Aposteriori
estimates and damage prevention
Anastasia Karakozova1
*
, Sergey Kuznetsov1,2, Vladimir Mondrus1, and Vladimir Bratov3
1Moscow State University of Civil Engineering, 26, Yaroslavskoye shosse, Moscow, 129337, Russia
2Ishlinsky Institute for Problems in Mechanics, 119526 Moscow, Russia
3Edinburgh Napier University, Edinburgh, UK
Abstract. The recent devastating earthquake of Mw7.8 occurred on
February 6, 20223 in the Kahramanmaraş region having extreme intensity
(XI) on the modified Mercalli scale (MMS) caused the death of more than
52,800 people in Turkey and Syria, as well as severe damages to the
infrastructure. The appearance of an unusually strong delta-like S-wave
pulse in the seismogram of the main shock and its consequences are
analysed, and possible measures to mitigate the possible future high
intensity earthquakes are discussed.
1 Introduction
The recent earthquake (06.02.2023) of Mw7.8 and the subsequent strong aftershock Mw7.5,
which took place in the Kahramanmaraş region of Turkey and in the nearby regions in
Syria, had a relatively shallow hypocentre located within the sedimentary layers of the
Earth’s crust, about 10,000 meters below the ocean level [1, 2]. The estimated earthquake
intensity in the cities Gaziantep and Kilis was XI on the modified Mercalli scale [3, 4]. The
aftershocks continue and are likely to continue for about a year after the main shock [3].
Fig. 1. Seismogram of the main shock at 01:17 GMT, Station IU ANTO, Ankara, Turkey.
*
Corresponding author: karioca@mail.ru
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© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative
Commons Attribution License 4.0 (https://creativecommons.org/licenses/by/4.0/).

The analysis of seismogram detected at different stations reveals the presence of a large
delta-like pulse located in Fig. 1 between 01:20 and 01:22. It is apparently associated with
the arrival of the horizontally polarized large intensity and short duration S-wave. The
authors’ estimates indicate the duration of the pulse being ~120 ms. The IU ANTO station
is located about 235 km away from the epicentre.
It should also be noted that the situation is much more typical when seismograms
recorded at remote stations do not contain large impulses of such a short duration; see a
sample of a typical seismogram in Fig. 2.
Fig. 2. The typical seismogram; an earthquake near island Severnaya Zemlya, occurred on
19 April 1997 [5]; red line indicates arrival of S-waves.
It should also be noted that the situation is much more typical when seismograms
recorded at remote stations do not contain large impulses of such a short duration; see a
sample of a typical seismogram in Fig. 2. However, such a short duration and large
amplitude pulses were also recorded primarily at the arrival of S-waves accompanying
some high intensity earthquakes [6]; see Fig. 3.
Fig. 3. A seismogram of the Kobe earthquake, occurred on 17 January 1995 [6].
2 What does a delta-like pulse spectrum look like?
Consider integral Fourier transform of a triangle delta-like pulse
 
~( ) ( ) exp )
T
T
t i t dt

     

(1)
where

is the circular frequency;
()t
is the triangle function having finite support in the
time-domain:
supp =( ; )TT
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,0
() ,0
t T T t
p
tT t t T
T
   

    

(2)
In Eq. (1)
p
is an amplitude multiplier. Applying transformation (1) to function (2), yields
~2
( ) sinc 2
T
T

    

(3)
where
 
sin
sinc t
tt

(4)
In view of (3), the magnitude of
~()
becomes; see Fig. 4.
Fig. 4. Fourier spectrum of triangle delta-like pulse.
The plot in Fig. 4 clearly indicates the substantial maximum at zero frequency.
3 AFC of a typical seismic isolating device
Suppose a building is equipped with a typical seismic isolating device, modelled by Kelvin
– Voigt model or a more refined Zener model, known also as the standard viscoelastic
model [7]. The governing equations for both Kelvin – Voigt and Zener models may be
represented in the Cauchy form [8]
( ) ( ) ( )
dt t t
dt   Y G Y U
(5)
where for Kelvin – Voigt model
 
0
( ) 0 1
( ) ; ; ( ) exp
( ) / /
xt
t t i t
v t k m m
   
   
   
 
   
Y G U U
(6)
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Herein,
()xt
is the deflection of a mass;
( ) ( )v t x t
;

is the viscosity of a dashpot;
k
is the stiffness of a spring;
m
is the vibration mass; and,
0
U
is the amplitude of an external
load. Note that
G
is a semi-stable matrix [8]. For Zener model with the auxiliary spring,
the corresponding parameters become
1
2
1
() 0 0 1
( ) ; / / 0
()
( ) / / 0
()
xt
t k k
xt
k k m k m
vt
 
 

    
 

 



YG
(7)
where
11
( ), ( )x t v t
are deflection and speed of the mass;
2()xt
is the deflection of the
auxiliary spring; and,
k
is the auxiliary spring stiffness.
Solving Eq. (6) at different excitation frequencies yields the amplitude-frequency
characteristic (AFC); the typical AFC for Zener model is shown in Fig. 5.
Fig. 5. The typical AFC of a seismic isolating device modelled by a linear Kelvin element
The plot in Fig. 5 clearly demonstrates that the typical seismic isolating device being
perfectly suited for damping relatively high frequencies (
2
), generates considerable
signal amplification in a smaller frequency range (
1
), exactly, where the delta-like
pulse spectrogram attains its maximum; see Fig. 4. Thus, the considered seismic isolating
devices become not only useless at low frequencies, but instead they amplify seismic
signals in the low frequency range.
4 Collapse of a frame building without seismic isolation
Consider now the diffraction of the high intensity seismic delta-like S-wave in a frame
building without seismic isolation.
The FE analysis of the diffracted large amplitude and short duration S-wave pulse
reveals, (i) appearing the high intensity stress fields in both columns and plates; (ii)
multiple damage zones mostly appearing at the back-fronts of the diffracted waves; and,
(iii) collapse of the frame elements prior to the onset of vibration, when the standing waves
are formed; see Fig. 6.
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Fig. 6. Collapse of the frame building caused by the arrival of shock waves of high
intensity; FE modelling
The slide in Fig. 6 demonstrates collapse of the building frame elements starting from
the bottom floors, while the high-intensity wave propagates upward in the building.
5 How to get seismic protection at arrival of high intensity shock
waves?
5.1 Seismic pads, an overview
A natural question arises, on how to become seismically protected at the appearance of high
intensity and short duration seismic pulses, similar to one appeared in the seismogram of
the considered Turkey – Syria earthquake on 06.02.2023; see Fig. 1. That is especially
important in view of the principal inability of the seismic isolating devices to damp such
short pulses; see Figs. 4 and 5.
Currently, there are several approaches for mitigating the effect the considered shock
wave pulses; some of these approaches are already developed, while others are still under
development. The already developed solutions include,
a) b)
Fig. 7. Seismic pads for protecting a) NPP reactor building with a granular seismic pad
against both P- and S shock waves below the foundation substructure [9]; b) splitting the
grillage with a seismic pad made of granular metamaterial (shown in red) [9].
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(I) One of the developed approaches relies on installing a seismic pad beneath the
foundation slab (Fig. 7a) or splitting the grillage, in the case of a pile foundation (Fig.
7b); see [9]. These seismic pads are made of granular metamaterials, ensuring (i)
reflection of the arriving seismic waves in a broad range of the corresponding spectral
frequencies; (ii) absorbing the mechanical energy of seismic waves inside of the
granular metamaterial; and (iii) the lifespan of the granular metamaterials comparable
or exceeding the lifespan of the protected structure due to the inorganic nature of the
granules.
(II) The organic granular materials for applications in the earthquake engineering are also
produced [10], however, they generally do not have as long a lifespan, as those made
from inorganic materials.
(III) Another solution used at constructing Rion-Antirion bridge and some other long-span
bridges [11], consists in a seismic pad made of calibrated natural stones and placed
beneath the grillage; the latter is separated from the pile field, ensuring horizontal
movement of the grillage and the pylon with respect to the ground.
(IV) Seismic pads especially constructed for seismic isolation of precision equipment, e.g.
the use of elastomeric sheets coupled with mechanical sliders [12].
Some other approaches that are currently being under development include,
(V) Seismic pads made of sheets of fluoroplastic, which have a very small friction
coefficient and serve for achieving almost friction-free sliding surfaces [13, 14]. This
approach can also be referred to the seismic protection by a meta-surface, since it is
based on the concept of a sliding surface.
(VI) Seismic pads made of the granular metamaterials and exhibiting properties of the
broadband phononic crystals and simulating by the modified Cam-clay model [15].
The main principle of this approach relies on dissipation of mechanical energy inside
the pad by using granular materials with low cohesion, which provide the
development of plastic deformations at the relative movements of the granules.
5.2 Seismic pads, basic principles
The considered seismic pads are capable for seismic protection from large intensity S-
waves in a broad frequency range, moreover, as was previously mentioned, some kinds of
pads are capable of protecting from P-waves. At least three basic principles ensuring the
efficiency could be stated,
(A) The acoustic impedance difference between ambient soil or concrete and granular
metamaterial used for a typical seismic pad (not applicable to seismic pads made of
fluoroplastic sheets). This principle ensures reflection of seismic wave energy at the
interface between seismic pad and soil or concrete, thus decreasing amount of the
wave energy diffracted into building. Note also that the reflection-refraction
coefficients do not depend upon wave frequency due to the Knott – Zoeppritz
equation.
(B) The appearance of the so called shock wave fronts in the microstructure of the granular
material, resulting in the dissipation of the wave energy inside the seismic pad . And,
the appeared shock wave fronts are almost insensitive to the diffracted seismic wave
frequency.
(C) The ability of relative movement of different granules inside the pad, which ensures
attenuation of the seismic wave energy.
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6 Concluding remarks
It is noted that the recent devastating earthquake of Mw7.8 occurred on February 6, 20223
in the Kahramanmaraş region and having extreme intensity (XI) on the modified Mercalli
scale (MMS) caused the death of more than 52,800 people in Turkey and Syria, as well as
severe damages to the infrastructure. Analysis of the seismograms revealed the appearance
of an unusually strong delta-like S-wave pulse in the seismogram of the main shock. As
was pointed out the observed delta-like pulse corresponds to a large peak located at the zero
frequency, making most of the widely used seismic isolating devices almost unusable, or
even dangerous, at the appearance of delta-like pulses, since, as was shown, the considered
seismic isolators amplify signals in the vicinity of zero frequency.
The analysis of the existing and being under development methods of seismic protection
based on different seismic pads containing granular metamaterials, revealed the major
benefits of these methods of seismic protection comparing to other types of seismic
isolation, especially in regard of the appeared strong delta-like pulses in the earthquake
seismograms.
The current research of (A.K., S.K., and V.M.) was supported by the Russian Ministry of Science and
Higher Education, grant FSWG-2023-0004.
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