Matemática Pura

Journal of Earthquake Engineering, 11:110–132, 2007 Copyright © A.S. Elnashai & N.N. Ambraseys ISSN: 1363-2469 print / 1559-808X online DOI: 10.1080/13632460601123164

Journal 1559-808X 1363-2469 UEQE of Earthquake Engineering, Vol. 11, No. 1, December 2006: pp. 1–29 Engineering

Seismic Microzonation and Damage Assessment of Bam City, Southeastern Iran
RAMIN MOTAMED

R. Motamed et al.Seismic Micronization, Damage Assessment of Bam, Iran

Department of Civil Engineering, The University of Tokyo, Tokyo, Japan

ABBAS GHALANDARZADEH
Department of Civil Engineering, University of Tehran, Tehran, Iran

IKUO TAWHATA
Department of Civil Engineering, The University of Tokyo, Tokyo, Japan

S. H. TABATABAEI
Geotechnical Department, Building and Housing Research Center, Tehran,Iran
This article aims to study the dynamic characteristics of soil in Bam, southeastern Iran. Fundamental frequency and amplification factor of soil sediment were estimated by microtremor measurement. This procedure was performed at 49 sites in the city. Two 120-second data were recorded at each site. Segmental cross spectra were applied to calculate spectrum, Nakamura’s method (H/V) was used foranalyzing data and fundamental frequency and amplification factor values were derived. Iso-frequency and iso-amplification maps of the city were prepared. Results show that soil type in Bam city is mainly stiff, although amplification factor is relatively large. There is a short period zone in northwest to southeast direction. Sediment depth was estimated using a correlation between fundamentalfrequency and sediment thickness. Results obtained from microtremors were compared to the geotechnical boreholes and it was shown that microtremors can be used for a rough estimation of sediment thickness. Damage distribution map of Bam due to the Bam earthquake on December 26, 2003 was prepared by both field and aerial investigation. Quality of buildings in Bam was evaluated, as a result a crudezoning map on the building quality was prepared. Finally, it was concluded that several factors have contributed to damage intensity variation; earthquake characteristics, local site effect, and buildings’ quality. All mentioned parameters affected the damage variation. Keywords City Microtremors; Fundamental Frequency; Amplification; Damage Variation; Bam

Received 17 May 2005; accepted 29 June2006. Address correspondence to Ramin Motamed, Geotechnical Engineering Laboratory, Department of Civil Engineering. The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan. E-mail: motamed@geot.t.u-tokyo.ac.jp

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1. Introduction
Safety against earthquake hazards has two aspects: firstly, structural safetyagainst potentially destructive dynamic force and secondly the safety of a site itself related with geotechnical phenomena such as amplification, landsliding, and liquefaction. In order to mitigate the risk from earthquakes, the first is accomplished by considering dynamic loading in the design process and the second is considered by using zoning maps based on geotechnical investigations. Severalattempts have been made to identify and appraise geotechnical hazards and to represent them in the form of maps. Generally, the outcome of a hazard assessment is presented on a zoning map in which locations or zones with different levels of hazard potential are identified. According to the TC4 manual [TC4, 1997], the zoning map may be used in land use planning or implementation of mitigative measures.Three grades of approach for zoning are described as follows based on the level of resolution. The first level of zonation (Grade-1) is the crudest and lowest-cost approach, while the third level (Grade-3) is the most expensive and requires detailed site-specific information. Microtremor measurement is classified in Grade-2 and can be utilized to obtain information on subsurface soil or...