modeling 3d faults for seismic hazard assessment in...
TRANSCRIPT
Agung Setianto1 and Ibrahim Djamaluddin2,
1Department of Geological Engineering, Gadjah Mada University, Indonesia
2Department of Environmental Engineering, Hasanuddin University, Indonesia
Modeling 3D Faults for Seismic Hazard
Assessment in GIS
Earthquake hazards...
Slope failures
A landslide triggered by an earthquake in Sichuan province, China;
2008
Seismic-induced fires
Buildings in flames as fire spreads by earthquake in Kobe,
Japan; 1995
Several well-known examples of destructive earthquakes have clearly shown that the local site conditions are an important factor
in determining the seismic hazard specific to a given site.
Structural damages
Nepal earthquake collapses buildings in
Kathmandu; 2015
Subsidence/settlements
Places were submerged under the sea surface, by Great Japan
Earthquake on April, 2011
Liquefaction
Liquefaction on Kilmore St., Newzealand by earthquake of 22 Feb
2011.
Flow of presentation Introduction to a Seismic Hazard Map
- Earthquake and seismic ground motion
- Types of earthquakes
- Types of seismic hazard maps
Seismic Hazard Maps for Specified Seismic Source 3D Faults
- Types of maps and related information
- Assessment methods
- Development of a GIS-based calculation system
Application
- Geological settings
- Historical seismicity
- Seismic hazard assessments
Earthquake and ground motion
An earthquake involves the shaking of the ground by vibrations caused by fault movements. The
characteristics of a seismic ground motion are depends on 3 factors:
1. source,
2. propagation, and
3. site condition.
The types of earthquakes
There are various types of earthquakes:
1. earthquakes on the plate boundary;
2. earthquakes within subducting (or subducted) plates; and
3. earthquakes occurring on active faults on land.
Types of seismic hazard maps
“Seismic Hazard Maps for Specified Seismic Source Faults” pay attention to
specific seismic source faults and indicate, the strong shaking of the
surrounding areas when an earthquake occurs.
1. conventional method, or
2. numerical simulation, such as FDM
"Probabilistic Seismic Hazard Maps” show the probability for a fixed time
period and intensity, and intensity for a fixed time period and probability.
1. probabilistic theory
Types of maps and related information
There are two types of "Seismic Hazard Map
for Specified Seismic Source Faults":
1. on the engineering bedrock, and
2. on the ground surface
Peak velocity on the engineering
bedrock
Peak velocity on the ground
surface
Seismic intensity on the
ground surface
Conventional method procedures
What is GIS?
Geoprocessing is a Python language consisting of operators, or tools, that operate on the data within
GIS, and perform tasks that are necessary for analyzing information across a wide range of disciplines.
What is Geoprocessing?
Development of an innovative assessment
system by GIS technology
applied Geoprocessing system to automatic computation of
the 3D geometric faults;
adopted the conventional method of seismic hazards to the
3D grid data calculation system; and
Customized calculation system interfaces tool.
GIS workflow process Peak velocity
eng. bedrock
Peak velocity
grd. surface
PGA
Seismic
intensity
Geology Lineaments 3D faults
Geomor-
fologic
Shear wave
Vs30
Amplifica-
tion factor
Grid data
system
3D fault process
3D seismic
analysis
Topography RS images
Input Process Output
Entire steps (110 processes)
1 step
Schematic workflows of geoprocessing
for automatic calculation of 3D faults
Example of input data
Dip 35
Dip 65
Fault line 1
Fault line 2
Integrated GIS interfaces
Interface for input data
Surface DEM (Raster
data)
Fault Line (Polyline
shapefile data)
Fault lines attributes
Depth of Fault
Fault Dip
Calculating interfaces
To be able calculation of many fault lines
by the iteration model
Result in 3D view
Result in 3D view
Developed seismic hazard system
Application to Beni suef, Egypt
The study area is located at the northern part of
Egypt as a part of the Nile Valley.
The study area is mostly covered by sedimentary
rocks of different formation as well characterized
by flat topography.
Generally, Egypt buildings are not designed
to resist earthquakes, therefore relatively small
events can be the source of huge disasters.
The earthquake of 12 October 1992 is well known example of a small but effecting
earthquake in Egypt. Local site effect conditions are directly related to significant damage and
loss of lives.
Geological conditions
A geologic map of the study area was
simplified from Egyptian General
Petroleum Corporation (1987), scale of
1:500,000
The area of Beni Suef is covered by
sedimentary rocks of different formations
belonging to the middle Eocene up to the
Quaternary.
Tectonic setting
The trend analysis of faults deduced from
geological and geophysical data around the
source area reflects the existence of two
dominant trends N60E and N45W (Abou
Elenean and Deif, 2003).
Based on analyzing the lineaments extracted
from geological map of EGPC (1987) in the
present study, it was observed that the prevailing
trends are dominantly in the NE-SW and
NW-SE, in correspondence with the previously
obtained trends deduced from geological map
and density map (Ammer, 1982).
Rose diagram
Relief map and lineaments
Shear wave velocity The shear wave velocity of shallow sediments is
very important in seismic wave amplification and
thus Vs30 is a well-known parameter for site
classification.
It has been recognized that soft and young
sediments covering firm bedrock can amplify
seismic waves and cause severe damage during a
large earthquake.
Qualitative estimation of susceptibility The areas where the soils consist of soft sediments
like loose sands and silty clay are more susceptible
to amplification.
It is obvious that lower shear wave velocities up to
400 m/s correspond quite well with the outcrop of
unconsolidated, Quaternary sediments in the study
area.
(Seed and Idriss 1982), mentioned that most soils
amplify peak acceleration where the hard ground
acceleration is less than 0.1g, where soft to
medium stiff clay and sand causing the largest
amplification.
Shear wave up to 400 m/s
Noted: (1.0g is approx. 980 cm/sec2 or 980 gals)
Recorded earthquake (1973~2010) around
study area by USGS
Study area
1992 Dahshour earthquake (5.9)
1999 Beni Suef earthquake (4.9)
3D faults and grid system in GIS
Scenario studies
Case 1: October 11, 1999 Beni Suef earthquake source
- magnitude 4.9,
- depth of epicenter 26km,
- fault depth to upper edge 15km,
- length of fault 5km, width of fault 12km, and
- fault orientation (strike153o and dip72o)
Case 2: October 12, 1992 Dahshour earthquake source
- magnitude 5.9,
- depth of epicenter 22km,
- fault depth to upper edge 12km,
- length of fault 12km, width of fault 10km, and
- fault orientation (strike 270o and dip47o)
Case 3: Case 2 with expected magnitude 6.5
Case 1: results
Case 1: results
Case 2: results
Case 2: results
Case 3: results
Case 3: results
Conclusion and Discussion Modeling 3D faults for seismic hazard assessment has been done in GIS. The
3D polygon as 3D fault layer was constructed automatically in GIS
geoprocessing process model by using a geometrical lines data. By 3D fault’s
shape and attribute data in the 3D polygon, GIS gives significant result for
the calculation of seismic hazard assessment in which the spatial data such as
3D fault layer, 3D topographical model can be applied in the GIS system
development.
Furthermore, seismic hazard assessment model for specified seismic source
faults as study case has been evaluated. The spatial ground motion of the
October 12, 1992 Dahshour earthquake with magnitude 5.9 and the
October 11, 1999 southeast Beni Suef with magnitude: 4.9 and maximum
expected parameters for earthquake source with magnitude 6.5 have been
simulated using the GIS developed system. The peak velocity on the
engineering bedrock, the peak velocity on the ground surface and the
seismic intensity on the ground surface are calculated.
Future research plan Seismic hazard maps
Geospatial maps
Disaster prevention and risk
reduction analysis