Simulation of an 1857-like Mw 7.9 San Andreas Fault Earthquake and the Response of Tall Steel Moment Frame Buildings in Southern California – A Prototype Study

In 1857, an earthquake of magnitude 7.9 occurred on the San Andreas fault, starting at Parkfield and rupturing in a southeasterly direction for more than 360 km. Such a unilateral rupture produces significant directivity toward the San Fernando and Los Angeles basins. The strong shaking in the basins due to this earthquake would have had significant long-period content (2-8 s), and the objective of this study is to quantify the impact of such an earthquake on two 18-story steel moment frame building models, hypothetically located at 636 sites on a 3.5 km grid in southern California. End-to-end simulations include modeling the source and rupture of a fault at one end, numerically propagating the seismic waves through the earth structure, simulating the damage to engineered structures and estimating the economic impact at the other end using high-performance computing. In this prototype study, we use an inferred finite source model of the magnitude 7.9, 2002 Denali fault earthquake in Alaska, and map it onto the San Andreas fault with the rupture originating at Parkfield and propagating southward over a distance of 290 km. Using the spectral element seismic wave propagation code, SPECFEM3D, we simulate an 1857-like earthquake on the San Andreas fault and compute ground motions at the 636 analysis sites. Using the nonlinear structural analysis program, FRAME3D, we subsequently analyze 3-D structural models of an existing tall steel building designed using the 1982 Uniform Building Code (UBC), as well as one designed according to the 1997 UBC, subjected to the computed ground motion at each of these sites. We summarize the performance of these structural models on contour maps of peak interstory drift. We then perform an economic loss analysis for the two buildings at each site, using the Matlab Damage and Loss Analysis (MDLA) toolbox developed to implement the PEER loss-estimation methodology. The toolbox includes damage prediction and repair cost estimation for structural and non-structural components and allows for the computation of the mean and variance of building repair costs conditional on engineering demand parameters (i.e. inter-story drift ratios and peak floor accelerations). Here, we modify it to treat steel-frame high-rises, including aspects such as mechanical, electrical and plumbing systems, traction elevators, and the possibility of irreparable structural damage. We then generate contour plots of conditional mean losses for the San Fernando and the Los Angeles basins for the pre-Northridge and modern code-designed buildings, allowing for comparison of the economic effects of the updated code for the scenario event. In principle, by simulating multiple seismic events, consistent with the probabilistic seismic hazard for a building site, the same basic approach could be used to quantify the uncertain losses from future earthquakes

Healthcare network operation in Iquique after the 2014, Pisagua earthquake

On April 1st, 2014, the 8.2 Mw Pisagua earthquake affected the population in the north of Chile and generated disruption of services in the region. The largest effects of the earthquake were observed in the city of Iquique, capital of the Tarapaca Region, where more than 80% of the population of the region lives. This research describes the response of the public healthcare network of Iquique after the earthquake, and aims to identify the principal factors contributing to the network resilience during the early response and recovery phase after the earthquake. Despite the large magnitude of the earthquake, the observed structural damage was minor in the five healthcare centers considered (i.e., the regional hospital and 4 Primary Healthcare Attention Centers, PHACs). However, disruption of services in the healthcare network was large and due mainly to the collapse of non-structural components. Overall, the proper response of the healthcare network of Iquique was heavily supported by the PHACs, which largely provided first-aid, containment, and low-complexity attention to the population, allowing the hospital to focus on more complex procedures. The findings of this study suggest that the resilience of the healthcare network system, besides the robustness of the network’s facilities and their critical units, is also highly dependent on the interrelations and interactions between them in early post-earthquake recovery phases

Impact on Chilean hospitals following the 2015 Illapel earthquake

In a post-disaster environment, hospitals play a critical role in healthcare services continuities to the population while effectively coping with eventual losses of functionality. These losses come from physical damage to the facility, loss of utility lifelines, failure in supply chains, and reduction of personnel. However, data describing the detailed performance of hospitals during past earthquakes are scarce. Consequently, following the 2015 Mw 8.3 Illapel earthquake in central Chile, an exhaustive field campaign was carried out in the Coquimbo region to collect substantial perishable data to describe physical damage to hospitals and functionality losses. This study presents first the baseline information obtained in nine surveyed government hospitals, including size, location and type of infrastructure. Then, the seismic impact was analyzed and classified to show the main physical structural and non-structural damage, lifeline interruptions, losses in hospital units, and variations in flow of patients and staff. Transfers, discharges and evacuations of patients that occurred after the event were also reported. We found that the earthquake did not affect strongly the healthcare service despite the fact that most of the structural and non-structural damage was localized in the largest regional hospital. The archival nature of the data collected may deepen our understanding of the post-earthquake healthcare system performance, which is very useful in improving disaster preparation and overall resilience

Interfacing Building Response with Human Behavior Under Seismic Events

The goal of this paper is to model the interaction of humans with their built environment during and immediately following a natural disaster. The study uses finite element simulations to evaluate the response of buildings under input ground motions and agent-based dynamic modeling to model the subsequent evacuation of building occupants in the study area immediately following the seismic event. The structural model directly captures building damage and collapse, as well as floor accelerations and displacements to determine nonstructural damage, injuries and fatalities. The goal of this research is to make connections between building damage and occupant injuries, with geographic automata as the information handler for the agent-based platform. This research demonstrates that human behavior and evacuation patterns can be evaluated in the context of realistic structural and nonstructural damage assessments, and that prior knowledge of evacuation patterns is critical for adequate preparedness of cities to severe earthquakes

Interfacing Building Response with Human Behavior Under Seismic Events

The goal of this paper is to model the interaction of humans with their built environment during and immediately following a natural disaster. The study uses finite element simulations to evaluate the response of buildings under input ground motions and agent-based dynamic modeling to model the subsequent evacuation of building occupants in the study area immediately following the seismic event. The structural model directly captures building damage and collapse, as well as floor accelerations and displacements to determine nonstructural damage, injuries and fatalities. The goal of this research is to make connections between building damage and occupant injuries, with geographic automata as the information handler for the agent-based platform. This research demonstrates that human behavior and evacuation patterns can be evaluated in the context of realistic structural and nonstructural damage assessments, and that prior knowledge of evacuation patterns is critical for adequate preparedness of cities to severe earthquakes

The Impact of the 22nd February 2011 Earthquake on Christchurch Hospital

The 22nd February 2011, Mw 6.3 Christchurch earthquake in New Zealand caused major damage to critical infrastructure, including the healthcare system. The Natural Hazard Platform of NZ funded a short-term project called “Hospital Functions and Services” to support the Canterbury District Health Board’s (CDHB) efforts in capturing standardized data that describe the effects of the earthquake on the Canterbury region’s main hospital system. The project utilised a survey tool originally developed by researchers at Johns Hopkins University (JHU) to assess the loss of function of hospitals in the Maule and Bío-Bío regions following the 27th February 2010, Mw 8.8 Maule earthquake in Chile. This paper describes the application of the JHU tool for surveying the impact of Christchurch earthquake on the CDHB Hospital System, including the system’s residual capacity to deliver emergency response and health care. A short summary of the impact of the Christchurch earthquake on other CDHB public and private hospitals is also provided. This study demonstrates that, as was observed in other earthquakes around the world, the effects of damage to non-structural building components, equipment, utility lifelines, and transportation were far more disruptive than the minor structural damage observed in buildings (FEMA 2007). Earthquake related complications with re-supply and other organizational aspects also impacted the emergency response and the healthcare facilities’ residual capacity to deliver services in the short and long terms

Seismic Loss Estimation Based on End-to-end Simulation

Recently, there has been increasing interest in simulating all aspects of the seismic risk problem, from the source mechanism to the propagation of seismic waves to nonlinear time-history analysis of structural response and finally to building damage and repair costs. This study presents a framework for performing truly “end-to-end” simulation. A recent region-wide study of tall steel-frame building response to a M_w 7.9 scenario earthquake on the southern portion of the San Andreas Fault is extended to consider economic losses. In that study a source mechanism model and a velocity model, in conjunction with a finite-element model of Southern California, were used to calculate ground motions at 636 sites throughout the San Fernando and Los Angeles basins. At each site, time history analyses of a nonlinear deteriorating structural model of an 18-story steel moment-resisting frame building were performed, using both a pre-Northridge earthquake design (with welds at the moment-resisting connections that are susceptible to fracture) and a modern code (UBC 1997) design. This work uses the simulation results to estimate losses by applying the MDLA (Matlab Damage and Loss Analysis) toolbox, developed to implement the PEER loss-estimation methodology. The toolbox includes damage prediction and repair cost estimation for structural and non-structural components and allows for the computation of the mean and variance of building repair costs conditional on engineering demand parameters (i.e. inter-story drift ratios and peak floor accelerations). Here, it is modified to treat steel-frame high-rises, including aspects such as mechanical, electrical and plumbing systems, traction elevators, and the possibility of irreparable structural damage. Contour plots of conditional mean losses are generated for the San Fernando and the Los Angeles basins for the pre-Northridge and modern code designed buildings, allowing for comparison of the economic effects of the updated code for the scenario event. In principle, by simulating multiple seismic events, consistent with the probabilistic seismic hazard for a building site, the same basic approach could be used to quantify the uncertain losses from future earthquakes

Modelamiento de la evacuación de un colegio en Iquique

Evacuating people from potential tsunami inundation zones as a result of large earthquakes in cities and towns along the shoreline is a critical and complex social activity that needs to be executed in very short time by people while coordinated by emergency offices. This research focuses in the evacuation process inside the buildings that are located in inundation zones, developing an agent-based model to simulate building evacuations. The methodology that was used integrates the physical effects of agent motion with different social behaviors that have been observed in real evacuations. The model was applied to a real evacuation drill of a school in the city of Iquique, in northern Chile. The flow rates and evacuation times that were measured in the drill were used to quantify the predictive capacity of the proposed model, obtaining differences of 13.6% and 5.9%, respectively. This ability to model human evacuations in a realistic way can be used in the future to wide variety of applications, including the prediction of concerns in the evacuation process of a building, and assess the positive effects of possible mitigation actions that communities and people can undergo to improve their emergency evacuation response