Part 1: 23 October 2011 Van-Tabanlı Earthquake

Geotechnical Field Observations

METU Reconnaissance Team Geotechnical Group

Z. Gülerce, K.Ö. Çetin, M. T. Yılmaz, N.H. Sarıhan, Y.S. Ünsever, S. Ünsal, S. Sağlam, M.A.

Sandıkkaya, M. Türkoğlu

Sites visited by the geotechnical engineering team:

Group 1

Group 2

Immediately after the mainshock, a reconnaissance team from METU Geotechnical Engineering Division visited Van, Erciş and many other small towns where most of the damage occurred.

Most of the liquefaction-related failures were observed in the near vicinity of the Lake Van.

Particle size distribution analysis results of samples taken from liquefied sites

Group 1

Group 2

Lateral Spreading observed in

Topaktas Village along Karasu

River

Failure of natural slopes in shores of Lake Van

Failure of natural slopes

Rock fall to Van-Ercis Highway

Van-Ercis Highway East Lane Slope Failure

Van-Ercis Highway East Lane Slope Failure

Possible circular failure surface from field observations

Possible center of circular failure surface

Soil type: SM, ϕ=22 ° Static FS=1.90Dynamic FS=1.01 and PGA=0.4g

Funding for the field trip was provided by METU and Earthquake Engineering Research Center which is highly appreciated.

We would like to thank to Van Yuzuncu Yil University and IMO for their support.

Visual material for this presentation is used in METU_EERC and GEER earthquake reconnaissance reports.

Part 2: Performance of NGA-W1 Ground Motion Model Predictions

on Recent Events in Turkey:

2010 Elazığ and 2011 Van Earthquakes

Zeynep Gülerce and Emre Akyüz

March 08, 2010 Elazığ-Kovancılar Earthquake (MW =6.1)

Ocurred on left-lateral strike-slip East Anatolian Fault (EAF) which is one of the two major active fault systems in Turkey42 people lost their lives and 137 were injured during the event

Figure taken from METU-EERC Preliminary Report

Prediction peformance of NGA-W1 Models at PGA:

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CB_2008 (TR-Adjusted)CB_2008 Elazığ Kovancılar mainshock

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BA_2008 (TR-Adjusted)BA_2008Elazığ Kovancılar mainshock

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ID_2008 (TR-Adjusted)ID_2008 Elazığ Kovancılar mainshock

BA 2008 CB 2008

ID 2008

Prediction peformance of NGA-W1 Models at PGA:

AS 2008

CY 20080.001

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AS_2008 (TR-Adjusted)AS_2008Elazığ Kovancılar mainshock

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CY_2008 (TR-Adjusted)CY_2008 Elazığ Kovancılar mainshock

Prediction peformance of NGA-W1 Models at 1 sec:

BA 2008 CB 2008

ID 2008

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BA_2008 (TR-Adjusted)BA_2008Elazığ Kovancılar mainshock

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CB_2008 (TR-Adjusted)CB_2008 Elazığ Kovancılar mainshock

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ID_2008 (TR-Adjusted)ID_2008 Elazığ Kovancılar mainshock

Prediction peformance of NGA-W1 Models at 1 sec:

AS 2008

CY 2008

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CY_2008 (TR-Adjusted)CY_2008 Elazığ Kovancılar mainshock

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AS_2008 (TR-Adjusted)AS_2008Elazığ Kovancılar mainshock

October 23, 2011 Van-Tabanlı Earthquake (MW =7.1)

Reverse mechanism (rare in Turkey)Only 3 recordings within 200 km from the mainshock Figure taken from Gülerce et al.,

2012

Prediction peformance of NGA-W1 Models at PGA:

BA 2008 CB 2008

ID 2008

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BA_2008 (TR-Adjusted)BA_2008Van_Mainshock

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CB_2008 (TR-Adjusted)CB_2008 Van_Mainshock

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ID_2008 (TR-Adjusted)ID_2008 Van_Mainshock

Prediction peformance of NGA-W1 Models at PGA:

AS 2008

CY 2008

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CY_2008 (TR-Adjusted)CY_2008 Van_Mainshock

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AS_2008 (TR-Adjusted)AS_2008Van_Mainshock

Prediction peformance of NGA-W1 Models at 1 sec:

BA 2008 CB 2008

ID 2008

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BA_2008 (TR-Adjusted)BA_2008Van_Mainshock

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CB_2008 (TR-Adjusted)CB_2008 Van_Mainshock

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ID_2008 (TR-Adjusted)ID_2008 Van_Mainshock

Prediction peformance of NGA-W1 Models at 1 sec:

AS 2008

CY 2008

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CY_2008 (TR-Adjusted)CY_2008 Van_Mainshock

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AS_2008 (TR-Adjusted)AS_2008Van_Mainshock

Is this result expected?? Due to the limitations of the PEER-NGA project and the missing parameters in The Turkey GM dataset, a very small number of ground motions recorded during the earthquakes occurred in Turkey was included in the NGA -W1 database (Chiou, 2008)

Event Name (ID)

Year Mw A&S 2008

B&A2008

C&B2008

C&Y2008

Idriss2008

Izmir (44) 1977 5.30 0 0 0 1 0Dursunbey (47) 1979 5.34 1 0 0 1 1Erzincan (121) 1992 6.69 1 0 1 1 0

Dinar (134) 1995 6.4 2 4 2 2 0Kocaeli (136) 1999 7.51 17 26 22 17 6Duzce (138) 1999 7.14 13 22 14 12 7

Caldiran (141) 1976 7.21 1 0 1 1 0Total 35 52 40 36 14

Number of recordings included in the dataset

Even though a large amount of data is available, a whole database with complete source metadata and recording station information was difficult to establish during the project.

4607 sets of ground motions recorded during the earthquakes occurred in Turkey between 1976-2007 were gathered and delivered through the project web-site.

daphne.deprem.gov.tr

TSGM database includes 4067 sets of recordings from 2996 events.Only 173 of these events are magnitude 5 or bigger.During these 173 events 685 recordings were taken.Small magnitude events (M<5) only if 3 or more recordings are available.The moment magnitude for 119 of events estimated from ML using Akkar et al. 2010No site information (Vs30 or site classification) could be found for 431 recordings (estimated from NGA-W1 database or removed)The style of faulting for 68 recordings are estimated from the mechanisms of other earthquakes in the sequence or due to the dominant mechanism of the region. If the distance measures were missing (96 recordings) they were estimated from the fault plane solutions or Rhypo and Repi values.

The starting point: TSGM (Daphne) Database

Final Comparison Dataset

Final Checks:Distance metrics with NGA-W1 databaseDepth to top estimationDeclustering (Thanks to Katie Woddell from PG&E)GmRotI50 consistency with the NGA-W1 database

Evaluating the Magnitude, Distance and Vs30 scaling of the dataset:

Residual Mean Offset

Event Term

Intra-Event Residual

+…

Turkey-Adjusted NGA-W1 Models: All five NGA-W1 models are evaluated using the

comparison dataset by analysis of model residuals. Inter-event residuals vs. magnitude plots showed

significant overestimation for small-to-moderate magnitudes! Corrected by adding adjustment functions for Mw<6.75.

Well-constrained pieces of the models (Mw>6.75) were preserved.

Turkey-Adjusted NGA-W1 Models: Intra-event residuals vs. distance plots suggested no

trend within the applicability range of the NGA-W1 models for tectonic regions other than Western US (100 kilometers)

The large distance scaling (gamma-term) were adjusted (100-200 km).

Turkey-Adjusted NGA-W1 Models: AS2008 and CY2008

models slightly under-predict the ground motions in the Turkey comparison dataset at stiff soil/engineering rock sites but this effect diminishes as Vs30 decreases. Aftershocks....

Corrected by adding adjustment functions for Vs30 >450 m/s.

5 new models for Turkey (TR-Adjusted NGA-W1 models) will be published soon. (Gülerce, Kargıoğlu and Abrahamson, 2013. Submitted to Earthquake Spectra).