Criteria for Surface Rupture Microzonation of Active Faults for Earthquake Hazards in Urban Areas

Criteria for Surface Rupture Microzonation of Active Faults for Earthquake Hazards in Urban Areas

Hasan Sözbilir (Dokuz Eylül University, Turkey), Çağlar Özkaymak (Afyon Kocatepe University, Turkey), Bora Uzel (Dokuz Eylül University, Turkey) and Ökmen Sümer (Dokuz Eylül University, Turkey)
DOI: 10.4018/978-1-5225-2709-1.ch005
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Abstract

Formation of surface rupture zone along active faults buried directly beneath major cities create devastating earthquakes that seriously threaten the safety of human lives. Surface rupture microzonation (SRM) is the generic name for subdividing a region into individual areas having different potentials hazardous earthquake effects, defining their specific seismic behavior for engineering design and land-use planning in case a large devastating earthquake strikes the region. The basis of SRM is to model the rupture zone at the epicenter of an earthquake, and thus develop a hazard-avoid map indicating the vulnerability of the area to potential seismic hazard. Earthquake hazard assessment of active faults in urban areas are thus an important systematic engineering for disaster mitigation in major cities.
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Introduction

Rapid urbanization all around the word in recent years, and destructive earthquakes occurred along tectonically active plate boundaries reveal the importance of active tectonic studies that investigates location and magnitude of earthquake(s); length of, and maximum slip rates along active faults; and earthquake recurrence intervals. Getting these parameters, which are essential for the earthquake hazard/risk assessment studies, highly requires careful mapping of active faults with priority by the expert field geologist(s). Nevertheless, because these deformations are mostly developed in poorly or un-consolidated Holocene sediments, surface trace of active faults may become unclear. Because of climatic conditions, erosional surface process or human activities, such as agricultural cultivation and urbanization, are tended to be erasing fault traces in easily erodible young sediments. During the past decades, the development of many new techniques, involving both surface and underground data for mapping of active faults at a scale of >1:10.000, especially in urban areas, provide convenience to field geologist. This chapter describes common multidisciplinary techniques, including geologic, geomorphologic, geophysic, paleoseismologic, geodetic, geoarchaeologic and hydrogeologic data, currently used during mapping of active faults. To do this, primarily the basic and important features related to the definition and mapping tools of the active faults will briefly be summarized. Then, information about how to make trench-based paleoseismological studies on the selected faults will be given. After that, how to set degree of surface rupture microzonation will be explained. Finally, the case studies from the Havran-Balıkesir Fault Zone, which is located at northern part of the Western Anatolian extensional province, will be presented.

Key Terms in this Chapter

Surface Rupture Microzonation: The generic name for subdividing a region into individual areas having different potentials hazardous earthquake effects, defining their specific seismic behaviour for engineering design and land-use planning in case a large devastating earthquake strikes the region.

Horizontal Location Uncertainty: It is a lateral uncertainty derived from the actual position of the future fault rupture due to fact that both data quality and personal skill/ability.

Surface Rupture: Surface rupture of an active fault is a zone of intense ground deformation on opposite sides of the active fault move past or over each other during an earthquake.

Asymmetric Buffer: It’s an additional safety band due to the effect of greater deformation focused in the hanging-wall blocks of both reverse and normal faults for asymmetric nature of deformation.

Fault Complexity: Fault complexity refers to the width and distribution of the deformed land around the fault trace. This term is also a criterion for how much the fault deformation zone is well defined.

Building Setback Distance: The required separation between the fault trace and the allowed area for construction.

Recurrence Interval: Interval of time in which a precipitation of a surface ruptured earthquake event is expected to occur once, on the average. In a broad sense, it is an average return time span of the earthquake occurrences on a fault zone.

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