6.3 Iran Earthquakes of August 11, 2012

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1 Learning from Earthquakes The M w 6.4 and M w 6.3 Iran Earthquakes of August 11, 2012 This report was contributed by members of the Iranian Earthquake Engineering Association (IEEA): Mohsen Ghafory- Ashtiany, Mehran S. Razzaghi, Mohammad Davoodi, Afshin Kalantari, Mohammad Tatar, Farokh Parsizadeh.Unless otherwise indicated, photos in this report were taken by team members. This report was edited by Sarah Nathe, EERI Newsletter Insert Editor. Introduction km from Ahar and Varzaghan. Both events had the same coordinates (38.41 N E) (Moradi, 2012) and the focal depths were determined at 9 km and 16 km, respectively. The focal mechanisms of both events are consistent with rightlateral strike-slip faulting on an E-W trending fault parallel to the South Ahar fault; field observation also revealed an E-W trending right-lateral strike-slip surface rupture (Figure 2). However, the second shock shows a considerable reverse component (Global CMT, 2012) On August 11th 2012 at 04:53 p.m. (local time), a M w 6.4 (NEIC) earthquake struck near the cities of Aharand Varzaghan in the East Azerbaijan province in northwest Iran. This quake was followed by another M w 6.3 earthquake 11 minutes later at 05:04 p.m. The local seismic network, Institute of Geo-physics, University of Tehran (IGTU), indicated the second quake was located just below the first at a depth of around 16 km. The earthquakes destroyed more than 20 villages and damaged the cities ofvarzaghan, Ahar, and Heriss. The earthquakes killed 327 people, caused more than 3,000 injuries, and left more than 30,000 homeless. Many adobe buildings in villages collapsed and several masonry and framed buildings were damaged. Roads were damaged by surface faulting and geotechnical instabilities; some bridges were damaged, but remained serviceable. Many essential facilities such as hospitals were damaged and some industrial plants were closed and suffered significant economic losses. Figure 1. The epicentral area of the twin earthquakes. Estimates of the main shock epicenters are shown as stars: red from the International Institute of Earthquake Engineering and Seismology (IIEES); green from the Institute of Geophysics at Tehran University; and blue from the USGS National Earthquake Information Center (NEIC) Seismology The twin earthquakes struck approximately 60 km northeast of Tabriz (Figure 1) and around 20 Figure 2. Surface ruptures indicating right-lateral strike-slip faulting (photos: Davoodi, Kalantari and Mostafazedeh, 2012) 1

2 (a) (b) Figure 3. Acceleration time histories of the second main shock recorded at the Varzaghan station: (a) largest transverse component; (b) vertical component (source: Building and Housing Research Center, 2012) The strongest SGM acceleration PGAs of the first and the second earthquakes were 0.427g and 0.534g (uncorrected records), respectively, recorded at BHRC- Varzaghan station. Figure 3 shows the acceleration time histories of the largest transverse and vertical components of the second main shock. The response spectra of the 2nd main shock are indicated in Figure 4. Long-period components are observed in the spectra of the ground motion during the second event; vertical components are also shown. As of the end of August, over 1000 aftershocks had struck the area, more than 100 of which were less than M 3 (Figure 5). Figure 6 shows the daily number of major recorded aftershocks within eight days of the earthquake. Geotechnical Aspects Several geotechnical instabilities such as landslides, sinkholes, liquefaction, and other site effects resulted from the earthquakes. Landslides: There were a number of earthquake-induced landslides, predominantly rock slides and falls (Mahdavifar and Memarian, 2012). The Pliocene lithology in some (a) (b) Figure 4. Response spectra of the second main shock (h is damping ratio): a) largest transverse component; b) vertical component (prepared by: A. Kalantri). Figure 5. The locations of the aftershocks recorded at local permanent stations of IGTU. A local temporary seismic network of 17 stations, installed by IIEES two days after the man shock, is shown as red triangles (source: IIEES, prepared by M. Tatar). 2

3 areas increased the sliding potential (Bandab Consulting Engineers, 1995); the earthquakes also reactivated some previous landslides. Figure 7 shows the distribution and types of different landslides in the stricken region. Figure 6. Number of major aftershocks until August 18, 2012 (source: ISNA, prepared by M. Razzaghi). Liquefaction: According to the liquefaction susceptibility map of Iran (IIEES, 2012), the stricken area has a low potential for liquefaction. Some limited liquefaction was observed near Marjanlar village, Lorik and Nosham weald, and near Kervigh village. No structural damage was caused by liquefaction (Mahdavifar and Memarian, 2012). Sinkholes: Two relatively large sinkholes induced by the earthquake were observed near Marjanlar and Merkid villages. The largest one had a 10 m diameter and 3 m depth, as shown in Figure 8. Its induced cracks radiated 15 m away. Topography and site effects: In Varzeghan, the greatest damage was observed in buildings next to the river. Generally, physical damages decreased with increased distance from the river. In Ahar, many of the damaged buildings were concentrated on hills (Figure 9). Performance of Residential Buildings Figure 7. The locations of the aftershocks recorded at local permanent stations of IGTU. A local temporary seismic network of 17 stations, installed by IIEES two days after the man shock, is shown as red triangles (source: Mahadavifar and Memarian, 2012). Most of the collapsed and damaged houses in the affected villages were adobe and unreinforced masonry buildings. The main failure modes were collapse of heavy roofs, inplane failure of walls, and out-ofplane failure of walls as shown (Figure 10). In general, performance of brick masonry buildings was better than that of adobe ones. Both framed (steel and RC) structures and brick masonry buildings are found in urban areas. No structural damage, and little nonstructural damage, was seen in residential buildings in Herris. However, resi- 3

4 Figure 8. Lateral spreading in Nosham weald (source: Mahadavifar and Memarian, 2012). Figure 9. A typical example of site and/or topography effects on a hill in Ahar City (source: Zare et al., 2012). Figure 10. Failure of heavy steel jack-arch and concrete roofs, and walls of unreinforced masonry buildings (photos: Mehr News Agency; Bastami). Figure 11. Performance of semi-steel frame buildings in villages (photos: Mehr News Agency; Bastami). 4

5 dential buildings of different types were damaged in both Ahar and Varzaghan. Infill walls in some buildings cracked in the northern parts of Tabriz. Most buildings that met minimum code requirements survived the earthquake, as shown in Figure 12. Performance of Essential Facilities Hospitals: The performance of hospitals was unacceptable. The main Heriss Hospital, with a RC moment-resisting frame, had some structural damage due to plastic hinges and the failure of many columns near the beam-to-column joint (Figure 13). All of the observed plastic hinges were located in the columns of the first floor. Some of the columns had shear cracks next to the openings of the infill walls. In addition to the aforementioned failures, diagonal cracks were observed in some of the beams next to the column joint. The main reasons for poor performance were slipshod construction methods, low-quality concrete, and insufficient bondage of cement paste and the aggregates. Figure 14 shows photos of nonstructural damage to the Herris Hospital: diagonal cracking and out-of-plane failure of infill walls, and failure of facades and false ceilings. The hospital was not operable after the earthquake. The Bagher-Al-Oloom Hospital in Figure 12. Buildings that met minimum code requirements performed well (photos: Mehr News Agency; Kalantari; Bastami) Figure 13. Herris Hospital structural damage:plastic hinges in beamcolumn joints (center) and diagonal crack in a column (bottom). 5 Figure 14. Nonstructural damage to Herris Hospital

6 Ahar also had extensive nonstructural damages and was put out of commission after the earthquake (Davoodi, Kalantari, and Mostafazedeh, 2012). In-plane failure of infill walls, failure of false ceilings, and overturning of medical equipment were the major problems. Universities: There was no observable structural damage in universities and dormitory buildings in Ahar, Varzaghan, or Herris. Several nonstructural failures were seen in educational and dormitory buildings at Varzaghan Islamic Azad University (IAU), a four-story steel-frame structure. Failure of infill and partition walls, damage to false ceilings, and overturning of unstable equipment and shelves were the major nonstructural failure modes. There were no deaths or injuries reported in the universities. Dams: The Sattarkhan, Yamchi, Herris, Sabalan and Khodafrin embankment dams and Shahryar concrete dam are the most important dams in the affected area. Only the Sattarkhan dam had damages, and they were minor (Figure 15). Some cracks in the upstream-downstream Downstream Upstream Figure 16 Casualties reported at different stages of the search and rescue operation (source: ISNA, prepared by M. Razzaghi). direction were observed, the intake tower of the dam was rotated slightly, and a 6 mm relative displacement was observed on the deck of the access bridge. Nonetheless, the dam was operable after the earthquakes because no evidence of abnormalities--including water discharge from the core and cutoff curtain--was observed. Roads and bridges: Although some of the bridges in the affected area had structural damage, all of the observed bridges were fully serviceable after the earthquake. The pavement of some roads cracked due to the fault rupture and geotechnical instabilities, but the roads were passable after the earthquake. Disaster Response Search and rescue was performed by survivors, NGOs, and governmental organizations. Just four hours after the earthquake 87 dead and 400 injured people had been found by search and rescue teams. The number of killed and injured people reported 48 hours after the earthquake is indicated in Figure 16, which shows the effectiveness of the search and rescue operation. The search/rescue teams were least active 7-13 hours after the earthquake, which was midnight to early morning. Most of the fatalities reported by hospitals were children and women (Figure 17). Figure 15. Damage to Sattarkhan embankment dam (source: Davoodi et al., 2012) Industrial plants and factories: Most of the important industrial plants and factories (petrochemical plant, refinery, cement factory) were located near Tabriz and Soufyan, more than 45 km away from the epicenters of the earthquakes. It is estimated that the PGA of the earthquake in this zone was less than 0.05g. No observable structural damage was reported in the industrial plants, but operations in some of the plants were partially stopped because they had protocols for shut-down in nearby earthquakes. 6 As hospitals were damaged and inoperable, much medical treatment Figure 17. Age and gender distribution of fatalities (source: ISNA, prepared by M. Razzaghi).

7 took place outside in temporary tents. Rescue teams had to transmit injured people to the hospitals of the nearby cities, but they were hampered by huge traffic jams on the Tabriz-Varzaghan, Tabriz-Ahar, and other primary roads in the affected area. The traffic jams were caused by the large number of volunteers trying to go to the affected areas to help with search and rescue. The earthquake caused great distress among about 2 million people in Azerbaijan province; many people slept outside for several nights, especially in Tabriz. The earthquakes made more than 30,000 people homeless, and they had to live in emergency shelters, as shown in Figure 18. Following the earthquakes, representatives of NGOs and self-motivated volunteers were present in large numbers; they provided for the essential needs of victims (Figure 19), and the affected people helped themselves as well (Figure 20). Shortcomings of the crisis management: Disaster managers were unable to control the heavy traffic, especially in the first days after the earthquakes. The traffic jams and some frenzied driving caused several car accidents, which claimed additional victims. Different organi- Figure 18. Displaced people had to live in emergency shelters (photos: Mehr News Agency). Figure 19. Food and water distribution (photos: Parsizadeh; Eskandari; Mehr News Agency). 7

8 zations presented conflicting statistics about the number of dead and injured people, but such inconsistencies are common in most disasters. The emergency shelters (tents) were not suitable for the climate of the affected area, where the nights get cold even in summer. Sanitary services in the emergency shelters were insufficient. Lastly, psychological counseling was not made available to the displaced and traumatized people. Figure 20. Where there s life, there s hope (photos: Mehr News Agency) References Bandab Consulting Engineers, Engineering Geology of Ahar Dam Site, Tehran, Iran (in Persian). Building and Housing Research Center, Ahar earthquakes of 11 August 2012 (East- Azerbaijan), (in Persian). Davoodi, M., A. Kalantari, and M. Mostafazadeh, Urgent Reconnaissance Report on Ahar Earthquake: Report No. 1, www. iiees.ac.ir (in Persian). Global CMT Project Catalog, Records: A and A, International Institute of Earthquake Engineering Seismology (IIEES), (8/12/2012). Liquefaction Susceptibility Map of Iran, Keefer, D.K., Landslides caused by earthquakes, Geological Society of America Bulletin 95 (4), Mahdavifar, M.R., and P. Memarian, Preliminary Reconnaissance Report on Geotechnical Aspects of the Varzeghan Earthquake, (in Persian). Moradi, A., (8/13/2012), Personal communication, IGTU Department of Seismology. Zareh, M., Kalantari, A., Ansari, A., Haghshenas, E., Davoodi, M., Mostafazadeh, M. (2012), Preliminary Reconnaissance Report on Triple Varzaghan-Ahar Earthquake, (in Persian) Zareh, M., and M. Shahvar, An Urgent Report on the 11 August 2012, Mw6.2 and Mw 6.1; Ahar Twin earthquakes in East Azarbayjan Province of NW Iran, 8