ground motion simulations at rapid response sites in istanbul, turkey mathilde bøttger sørensen 1,...
DESCRIPTION
This study Hybrid method for simulating ground motions due to finite-extent earthquake source in Marmara Sea Pulido and Kubo (2004): Deterministic at low frequencies, semi-stochastic at high frequencies Simulation on irregular grid of Istanbul Earthquake Rapid Response and Early Warning System stationsTRANSCRIPT
GROUND MOTION SIMULATIONS AT RAPID RESPONSE SITES IN
ISTANBUL, TURKEY Mathilde Bøttger Sørensen1, Nelson Pulido2,
Anibal Ojeda3, Kuvvet Atakan1, Mustafa Erdik4
1Department of Earth Science, University of Bergen, Norway, 2Earthquake Disaster Mitigation Research Center EDM, NIED, Kobe, Japan, 3INGEOMINAS, Bogota, Colombia, 4Kandilli Observatory and Earthquake Research Institute, Bogazici University, Istanbul, Turkey.
Westward migration of earthquakes on the NAF
after Barka et. al. (2002)
This study• Hybrid method for simulating ground motions
due to finite-extent earthquake source in Marmara Sea
• Pulido and Kubo (2004): Deterministic at low frequencies, semi-stochastic at high frequencies
• Simulation on irregular grid of Istanbul Earthquake Rapid Response and Early Warning System stations
Istanbul Earthquake Rapid Response and Early
Warning System
Rapid Response system• 100 accelerometer stations• When triggered, station produces spectral
acceleration at a number of frequencies, 12 Hz filtered PGA and PGV
• Data sent pr SMS every 20 s• Main data center produces shake, damage
and casualty maps, which are available to the end-users within 5 min
Istanbul Earthquake Rapid Response and Early
Warning System
Early Warning system• 10 accelerometer stations close to the
Marmara fault • When several stations triggers an
alarm is declared • Alarm level is sent to critical facilities,
which can then shut down before the earthquake strikes
Use of simulation results
• Calibration of Rapid Response system parameters
• Calibration of Early Warning system parameters • Realistic scenario input for producing shake,
damage and casualty maps• Comparison to recorded earthquakes
Ground motion evaluation from asperity model
Ground motion simulation technique
• Low frequency: Deterministic wave propagation from an asperity model in a flat layered velocity structure (Discrete Wave Number Method, Bouchon 1981)
• High Frequency: Semi-Stochastic Simulation based on an asperity model . The model combines the stochastic methodology of Boore (1986) with the empirical Green’s function method of Irikura (1986), and a high frequency radiation pattern model (Pulido et. al 2002).
Scenario earthquake
Active tectonic map of the Marmara Sea (Okay et. al 2000)
Source parametersTotal seismic moment M0 = 2.0·1020 Nm
Asperity area Sa/S = 0.22
Average stress drop 5 MPa
Asperity stress drop 10 Mpa
Rise time Random, average 3.0 s
Rupture velocity Random between 2.8 – 3.2 km/s
fmax 10 Hz
Q 100 · f1.5
Velocity model
PGV results
PGA results
PGV
PGA
Waveform exampleAvcilar district
GM3D
Tectonic Setting Marmara Sea Region
Okay et. al 2000
Scenario Earthquake
Active tectonic map of the Marmara Sea (Okay et. al 2000)
Scenario Earthquake 1b
Active tectonic map of the Marmara Sea (Okay et. al 2000)
Scenario Earthquake 2
Active tectonic map of the Marmara Sea (Okay et. al 2000)
Scenario Earthquake 3
Active tectonic map of the Marmara Sea (Okay et. al 2000)
High Frequency Radiation Pattern Model
P-wave SH-wave SV-waveLow
Frequency
< 1HzNon-spherical
HighFrequencySpherical
> 3 HzThe region between 1 to 3 Hz is a transition between the theoretical radiation of a double couple to a completely stochastic radiation
Asperities and Seismicity
After Gurbuz et. al. (2000), Tectonic fault model from Okay (2000)
Fault Segments Parameters
Hypocenter located at a depth of 10 km
The depth seismogenic zone is 20 km
Variability of the Simulated Ground Motion
Simulated Spectra and Turkish Seismic Code
Turkish Seismic Code, Aydinoglu (1998)
Deterministic vs Probabilistic PGA Distribution
PGA values for a 10% of excedance in 50 years (Atakan et. al. 2002)
PGA from scenario earthquake 1a
Avcilar district
Sultanahmet district