ground motion simulations at rapid response sites in istanbul, turkey mathilde bøttger sørensen 1,...

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