=Paper=
{{Paper
|id=Vol-1839/MIT2016-p02
|storemode=property
|title= Evaluation of seismic hazard using seismic microzonation techniques
|pdfUrl=https://ceur-ws.org/Vol-1839/MIT2016-p02.pdf
|volume=Vol-1839
|authors=Evgeniy Bodyakin,Sergey Peretokin,Konstantin Simonov
}}
== Evaluation of seismic hazard using seismic microzonation techniques==
https://ceur-ws.org/Vol-1839/MIT2016-p02.pdf
Mathematical and Information Technologies, MIT-2016 — Information technologies
Evaluation of Seismic Hazard Using Seismic
Microzonation Techniques
Evgeniy Bodyakin1 , Sergey Peretokin2 , and Konstantin Simonov1
1
Institute of Computational Modeling of Siberian Branch of the Russian Academy
of Sciences,
Akademgorodok, ICM SB RAS, 660036, Krasnoyarsk, Russia
bodyakinevgeniy@gmail.com, simonovkv@icm.krasn.ru
2
Krasnoyarsk Branch Office of the Institute of Computational Technologies of the
Siberian Branch of the Russian Academy of Sciences – Special Designing and
Technological Bureau Nauka,
Mira avenue 53, 660049, Krasnoyarsk, Russia
ec ropr@mail.ru
Abstract. It was shown the technique of seismic hazard assessment
based on comprehensive use of methods of seismic microzonation.
This technique consists of four steps. The first step is to collect geolog-
ical, seismological, geophysical and topographic information. Each layer
according to geological engineering survey and geophysical work are as-
signed physical and mechanical properties (density, limit shear stress)
and the P- and S- wave velocity. Next (step 2) after visualization and
examination input data using GIS technologies 3D modelling of the geo-
logical environment is performed (it is created a grid each point of which
is referred to coordinates of the site). The number and depth of soil
are set in each point based on geological drilling data. Then (step 3) at
each point seismic intensity are calculated using instrumental methods
including the method of acoustic impedance and computer simulation
(GRUNT program). At the last stage according to the analysis of the
results of theoretical and instrumental methods seismic microzonation
map are created using GIS technologies. The procedure of constructing
maps uses different methods of selection areas with the same seismic
hazard (kriging, spline interpolation).
Keywords: earthquake, seismic microzoning, seismic intensity, GIS.
1 Introduction
Seismic microzonation is performed to quantity the influence of soil properties on
seismic vibration within the area of specific facilities and within the residential
areas. Selection of areas with different seismicity is carried out using compre-
hensive study of seismic properties of soils, geotechnical, hydro-geological and
seismotectonic features of the territory. As a result, after performing seismic
zoning the map of microzonation is created.
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Mathematical and Information Technologies, MIT-2016 — Information technologies
The technique of carrying out seismic microzonation can be divided into
four steps. The first step (preparing) includes acquisition of geological, seismic,
geophysical and topographic data. According this data 3D site model is created
(the second step).
The third step is calculation of seismic intensity in each model point of site
using instrumental and calculation methods of soil seismic properties assessment
[1, 2]. The following methods are used when seismic hazard is estimated:
∙ Seismic microzonation using acoustic impedance method
∙ Seismic microzonation using earthquakes and explosions records
∙ Seismic microzonation using microtremors
These methods are normative methods and are subjected in [2].
The basis of numerical simulation of the geological environment reaction to
strong earthquakes is the concept of the heed to take into account more than one
possible earthquake effect, so ensemble of earthquakes effect with different spec-
tral characteristics is estimated. Therefore for each model point of site numerical
simulation is implemented on the full range of accelerograms.
Numerical simulation lets us to carry out calculation of peak ground accel-
eration, time stress and strain changes, Fourier spectra and response spectra on
the site surface for a given input motion.
The final stage of seismic microzonation is creation of seismic microzonation
maps that displays the regions with varying seismic intensity. Seismic micro-
zonation maps provide the basis for seismic resistant construction, public safety,
environmental protection and other actions aimed to reducing the damage caused
by strong earthquakes.
2 Data acquisition
Reliability of hazard estimates directly depends on the quality and completeness
of the initial engineering-geological and engineering-geophysical information in
study area. In this regard, in the first step of seismic microzonation are used a
complex engineering geophysical method to determine the characteristics of the
ground layer, necessary to the implementation of instrumental and calculation
methods of seismic microzonation.
Geological information consists of drilling data: coordinates, absolute eleva-
tion, thickness and a number of layers, the groundwater level. This information
is taken from the geological engineering survey reports.
Each layer is assigned a number of engineering-geological elements (EGE).
The EGE is some amount of ground with the same name-bearing type and
uniform in properties and state. According to the EGE number each layer is
assigned physical and mechanical properties (density, critical shear stress, etc.)
and velocity of P- and S- waves. The velocities are obtained by processing and
interpretation of seismic exploration materials (complex method of refracted
waves, vertical seismic profiling). The abovementioned data should be presented
as database or spreadsheet for further work in GIS. The example of input data
is shown in Table 1.
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Mathematical and Information Technologies, MIT-2016 — Information technologies
Table 1: Example of one borehole input data
Borehole layer EGE X Y Z depth, m density Vp Vs
18 1 1 26436.6 21227.09 37.95 1.8 1.92 232 158
18 2 2 26436.6 21227.09 37.95 4.7 2.15 352 159
18 3 4 26436.6 21227.09 37.95 8 2.54 1025 488
18 4 5 26436.6 21227.09 37.95 10 2.72 2960 1968
At the same stage import and visualization of the boreholes data in the GIS
environment are implemented. In addition to this information topographic data
is displayed: lines of surface height, site boundaries, position of existing and
planned buildings on site (Fig. 1).
Fig. 1: Primary visualization of the input boreholes data
In most cases the input boreholes data may include data related to larger
area than the area on which seismic microzonation is performed. Selection of the
necessary data is carried out using GIS software tools which provide opportu-
nities for the use of graphical tools, in particular, to highlight the geographical
boundaries of site.
One more necessary data array for numerical simulation of the geological
environment reaction to strong earthquakes is set of synthesized accelerograms
or analogue accelerograms.
Calculated seismic impact can be modeled using accelerograms scaled to
strength-level event (SLE) or ductility-level event (DLE). The accelerograms
can be obtained from the following:
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Mathematical and Information Technologies, MIT-2016 — Information technologies
∙ from time-history of earthquakes obtained on building site or development
area
∙ from time-history of earthquakes obtained on regions that have seismotec-
tonic, geologic and other seismological conditions similar with area of site
∙ synthesized time-history of earthquakes based on parameters of seismic im-
pact for SLE and DLE
Time-history of earthquakes obtained on building site or development area
scaled to SLE and DLE.
During whole period of field geophysical works in area of building site is
carried out registration of seismic events from nearby seismogenic zone. The
time-history of earthquakes obtained on site are scaled to SLE and DLE.
Time-history of earthquakes obtained on regions that have seismotectonic,
geologic and other seismological conditions similar with area of site.
Ensembles of digital accelerograms of real seismic events obtained on regions
that have seismotectonic, geologic and other seismological conditions similar with
area of site are selected on the basis of SLE and DLE parameters (hypocentral
distance and magnitude) obtained in detail seismic zoning. For this purpose are
used databases contained time-history of real seismic events, for example the
database of accelerograms of Japan seismic station (http://www.kik.bosai.
go.jp/kik/search/index_en.html). When the accelerograms are selected from
the database engineering-geological conditions, hypocentral distance and mag-
nitude are taken into account.
Synthesized time-history of earthquakes based on parameters of seismic im-
pact for SLE and DLE.
Synthesized accelerograms are calculated using programs SMSIM [4] for mod-
eling synthesized time-history of earthquakes. The programs SMSIM are based
on simulation of ground motion using the stochastic method. It is very conve-
nient for modeling ground motion on studied site in engineering frequency band
from earthquake with given parameters hypocentral distance and magnitude
of earthquake. This method is taken into account regional features of seismic
source as well as influence of the features of the geological environment on the
propagation of seismic waves from the source to the site.
3 Building of geological 3D model of site
For the further computation on the basis of aforementioned date building of 3D
model points of geological environment is carried out with certain step.
Using GIS tools a grid is created and each point of which is geographically
linked height and coordinates of the site. Then each point is defined by the thick-
ness and a number of layers based on drilling data and engineering stratigraphic
columns (Fig. 2). These data are input for the subsequent calculation of seismic
intensity.
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Mathematical and Information Technologies, MIT-2016 — Information technologies
Fig. 2: 3D model of geological environment
4 Seismic intensity calculation
Seismic intensity calculation is carried out using acoustic impedance method and
programs calculating the oscillation of surface. There are various methods for
calculating the vibrations of layered soils based on linear equations [1] ; in this
paper is used program GRUNT, which is based on the method of thin-layered
media.
4.1 Seismic microzonation using acoustic impedance method
Instrumental evaluation of the velocity properties of site is considered as in-
formational base for calculation of seismic intensity increment. Estimation of
seismic intensity increments based on acoustic impedance method is carried out
based on measuring the velocities of seismic waves and the density values in 10
meter soil thickness of studied aria and reference soil.
The calculations are carried out according to the equation:
𝐼 = 𝐼0 + 𝛥𝐼𝑆 + 𝛥𝐼𝐵 , (1)
where 𝐼 is seismic intensity based on local conditions, 𝐼0 is initial seismic
in relation to the average ground conditions (II-category in seismic properties)
according to the detail seismic zoning; 𝐼𝑆 is seismic intensity increment because
of acoustic impedance differences in the target and the reference soil:
𝛥𝐼𝑆 = 1.67 log(𝑉(𝑝,𝑠) 𝜌𝑅 /𝑉(𝑝,𝑠)𝑖 𝜌𝑖 ), (2)
where 𝑉(𝑝,𝑠) and 𝑉(𝑝,𝑠)𝑖 are weighted mean value of the propagation velocities
of P- and S waves on the target and the reference soil, 𝜌𝑅 and 𝜌𝑖 are weighted
mean value of density in the target and the reference soil; 𝛥𝐼𝐵 is seismic in-
tensity increment because of deterioration of seismic properties caused by water
saturation.
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Mathematical and Information Technologies, MIT-2016 — Information technologies
4.2 Seismic microzonation using earthquakes and explosions records
Synchronous registration of earthquakes on the different parts of site provides a
simple way to compare some properties of ground motion. In this approach direct
problem of seismic microzonation is solved, i.e. seismic intensity increment in
some areas of site selected according to engineering-geological study is estimated.
After getting synchronous time-history of earthquakes frequency-domain char-
acteristics and seismic intensity increment with respect to the recording station,
located on the reference ground are estimated.
Seismic intensity increment assessment is carried out according to the equa-
tion [2]:
𝐴𝑖
𝛥𝐼 = 3.33 log( ), (3)
𝐴0
where 𝐴𝑖 and 𝐴0 are the average amplitude of ground motions (from one
earthquake) on the target and the reference soil respectively.
In many cases such assessment is not enough spectral analysis of the events
is carried out. The seismic intensity increment is defined for the entire frequency
range from 0.1 to 10 Hz, and separately for the low, mid and high frequencies.
Figure 3a shows the three-component record of ground motion of the regional
earthquake registered on the base station situated on I-category soil and station
4 situated on II-category soil. Figure 3b shows the Fourier spectra of these events
(root mean square was taken from three component records).
Fig. 3: Three-component record of ground motion on the two stations (a) and Fourier
spectra of records (b)
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Mathematical and Information Technologies, MIT-2016 — Information technologies
4.3 Seismic microzonation using microtremors
This method is used as supplementary method in seismic microzonation.
To assess changes of strong earthquake intensity using peak of microtremors
at a given period the following equation is used [2]:
𝐴𝑚𝑎𝑥𝑖
𝛥𝐼 = 2 log( ), (4)
𝐴𝑚𝑎𝑥0
where 𝐴𝑚𝑎𝑥𝑖 𝐴𝑚𝑎𝑥0 peak amplitude of microtremors on the target and
the reference soil respectively.
All calculations are performed using the seismic processing program Geopsy
(http://www.geopsy.org). Average Fourier spectra with duration from 40 to 60
second on the interval of 10 minutes or more (depending on the recording quality
noisy areas can be excluded) are calculated. All spectra are previously smoothed
by the Horse and Omachi window [Konno, K. and Omachi, T., 1998, Bull. Seism.
Soc. Am., 88, 228-241.] with a coefficient characterizing the bandwidth, b = 90.
Each piece of the recording also is multiplied by 5% weight cosine function to
reduce boundary effects.
Based on analysis of the fundamental frequency of the site maximum value
of spectra is selected in a particular bandwidth. The last step is to calculate
the seismic intensity increment using equation (4) relative to the base point.
It should be noted that in microtremors formation along with natural sources
involved numerous artificial sources, the impact of which cannot be controlled.
Inability to comply with the necessary conditions of registration microtremors
and strong variation of maximum amplitude values limit the use of microtremors
to calculate seismic intensity increment. Thus, the use of method of microtremors
registration is only suitable in combination with other instrumental methods.
4.4 Numerical simulation
One of the simplest one-dimensional soil models is KelvinVoigt viscoelastic model.
Shear stress 𝜏 in this case depends on the strain 𝛾 and its derivative 𝛾˙ as shown
below:
𝜏 = 𝐺𝛾 + 𝜂 𝛾,
˙ (5)
where 𝐺 is shear modulus, 𝜂 is viscosity.
Schematic representation of KelvinVoigt model is shown in Figure 4.
The dynamics of the soil environment is described by the following equation:
𝜕𝜏 𝜕2𝑢
=𝜌 2 (6)
𝜕𝑧 𝜕𝑡
Substitute the value 𝜏 from (3) and taking into account that 𝛾 = 𝜕𝑢
𝜕𝑧 ,
𝜕2𝑢 𝜕2𝑢 𝜕3𝑢
𝜌 2
=𝐺 2 +𝜂 2 (7)
𝜕𝑡 𝜕𝑧 𝜕𝑧 𝜕𝑡
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Mathematical and Information Technologies, MIT-2016 — Information technologies
Fig. 4: Schematic representation of KelvinVoigt model
To calculate the spectral characteristics and accelerograms on the surface or
in the interior of the multilayer inelastic (with absorption) media with plane
boundaries is used thin-layered media (The Schmidt Institute of Physics of the
Earth of the Russian Academy of Sciences). It is solved the two-dimensional
problem of propagation of plane bodily waves in nonelastic layer pack with free
upper boundary and underlying elastic half-space. From half-space to the lower
boundary layer thickness at an arbitrary angle it is fallen P- or S- wave with
unit amplitude at a given frequency, or wave with a given arbitrary shape. The
model parameters are thickness and density of layers, P- and S- wave velocity,
damping ratio. It can be used different models of the absorption mechanism in
the medium (linear dependence of the absorption coefficient on the frequency or
dependence described a linearly inelastic Gurevich model).
Output data depending on the conditions of the problem are obtained as
follows:
∙ The amplitude-frequency characteristics of a subsurface formation according
to a predetermined model
∙ Accelerograms on the free surface or inside the medium
∙ Seismic intensity increments calculated using relationship of the amplitude-
frequency characteristics of the studied and reference models
∙ Response spectrum corresponding to the calculated accelerograms
This method is implemented in Grunt software. The algorithms have been
adapted for problems of seismic microzonation allowing counting large amounts
of information in an automatic mode.
Geological section is described as a set of enumerated and numbered from
top to bottom layers (including the half-space) each of which has its mechanical
parameters. Each layer can be divided into sub-layers of equal power with its
mechanical layer parameters to determine the properties of motion in certain
depth (all calculations are executed in the program for the top of layer).
Input motion is read from formatted files. The nonlinear and inelastic soil
behavior under loads caused by strong movements is described by change in the
modulus of elasticity and damping, which are due to deformation. Their values
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Mathematical and Information Technologies, MIT-2016 — Information technologies
are determined iteratively by leading maximum deformation to a uniform one
to the entire layer.
For each model, automatic calculations are carried out using the synthesized
accelerograms [3, 4], analogue accelerograms and regional records of earthquakes.
The results of each calculation are numerical characteristics.
For each calculated pair (seismic event - model) are calculated set of charac-
teristics including:
∙ Peak ground acceleration (PGA) expressed in g defined for a given return
period (the maximum value of the modulus of the acceleration during earth-
quake)
∙ Response spectra calculated to the surface of site
∙ The duration of ground motion for a given return period;
∙ Period of oscillation with PGA;
To convert the peak acceleration in the seismic intensity the following equa-
tion is used[5]:
𝐼 = 2.5 log(𝑃 𝐺𝐴) + 1.25 log(𝑑) + 1.05, (8)
where 𝑃 𝐺𝐴 is peak ground acceleration expressed in 𝑔, 𝑑 is duration of
ground motion expressed in 𝑠𝑒𝑐𝑜𝑛𝑑.
5 Creation of seismic microzonation maps
The final stage of seismic microzonation is creation of seismic microzonation
maps based on analysis of the results of numerical and instrumental methods.
Creation contour seismic microzonation maps is performed using the grid
with certain step (usually 25x25 meters). Nodes of the grid are assigned design
parameters of seismic effects corresponding to zoning areas.
Based on the grid interpolation is performed and then surface in geotif format
is received. The user may make use of various options for surface contouring
(e.g. kriging, spline) offered by the GIS software. Because of the uniform grid
REGULARIZED type of spline is used. This type creates a smooth, gradually
changing surface.
The next step is to reclassify a raster values. The interval of raster values is
assigned the mean value. The step of interval is taken equal to integer value of
seismic intensity, and 0.1 of one.
After receiving the parameterized raster conversion to GIS polygons of this
raster is performed. Groups of raster pixels with the same values of seismic
intensity are combined into a single polygon with assigning this value of seismic
intensity (Fig. 5)
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Mathematical and Information Technologies, MIT-2016 — Information technologies
Fig. 5: Creation of seismic microzonation maps in GIS
6 Conclusion
The developed technique facilitates and accelerates research associated with seis-
mic microzonation.
Creation of the 3D geological environment model lets us to increase the ac-
curacy of defining seismic intensity of site.
Seismic intensity calculation is perfumed using instrumental methods and
numerical simulation. GIS is the primary tool for creating seismic microzonation
maps which is the final step of developed computational technique.
References
1. Zaalishvili V.B. Seismic microzonation of urban territories, settlements and large
building sites / V.B. Zaalishvili ; [ed. By Nikolaev] ; Center of Geophysical Investi-
gations of Vladikavkaz Scientific Center of RAS. Moscow: Nauka, 2009. 350 p.
2. RSN 60-86 Engineering survey for building. Seismic microzonation. Standards of
production work.
3. Boore, D. M. Simulation of ground motion using the stochastic method, Pure and
Applied Geophysics 160, 2003, 635-675 p.
4. Boore, D.M. SMSIM Fortran Programs for Simulating Ground Motions from Earth-
quakes: Version 2.0 A Revision of OFR 96-80-A , U.S. Geological Survey Open-File
Rep., 00-509, 2000. (http://geopubs.wr.usgs.gov/open-file/of00-509/).
5. Aptikaev F.F. Instrumental scale of seismic intensity. M.: Nauka I obrazovanie,
2012. 176 p.
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