THE ROLE OF THE GEOLOGIST IN EARTHQUAKE LOSS ESTIMATION: A CASE STUDY IN NORTHERN CALIFORNIA

A typical loss estimation process due to earthquake ground motion requires input from various sources. The two main requirements are the seismic hazard, including the location, duration, attenuation, and recurrence of earthquake events, and the inventory exposure characteristics of the region. Inventory exposure includes the building stock characteristics (e.g., building height, year of construction, structure type, occupancy class) and the lifeline infrastructure's relevant information (e.g., network distribution, year of construction, component location and material). From these two inputs, the damage to the inventory and subsequent loss is calculated.

Therefore, the earthquake loss estimation (ELE) process is interdisciplinary in nature, incorporating information from numerous experts. These individuals include geologists, seismologists, and civil and structural engineers. Furthermore, many stakeholders, including the insurance industry and governmental agencies, use the results of an ELE analysis to prepare for significant earthquake events.

This paper focuses on the role the geologist plays in the earthquake loss estimation process and how his expertise impacts the cost-effectiveness of earthquake mitigation. A case study is presented, using the HAZUS loss estimation software and analyzing the Oakland, California region. The study examines the uncertainty in the parameters developed by geologists and earth scientists and utilized in the modeling process. Specifically, the uncertainty in earthquake ground motion attenuation and soil classification mapping schemes in the region are analyzed under a variety of scenario earthquake events. The impact of these parametric and modeling assumptions on the direct economic losses to the region's residential structures is presented. Individual scenario events are highlighted, as well as the overall loss exceedance probability (EP) curves. Finally, the paper demonstrates how uncertainty in these parameters impacts the cost-effectiveness of structural mitigation measures for the residential property owner.