The ShakeOut Scenario: A Hypothetical M_w7.8 Earthquake on the Southern San Andreas Fault

Abstract

In 2008, an earthquake-planning scenario document was released by the U.S. Geological Survey (USGS) and California Geological Survey that hypothesizes the occurrence and effects of a Mw7.8 earthquake on the southern San Andreas Fault. It was created by more than 300 scientists and engineers. Fault offsets reach 13 m and up to 8 m at lifeline crossings. Physics-based modeling was used to generate maps of shaking intensity, with peak ground velocities of 3 m/sec near the fault and exceeding 0.5 m/sec over 10,000 km2. A custom HAZUS®MH analysis and 18 special studies were performed to characterize the effects of the earthquake on the built environment. The scenario posits 1,800 deaths and 53,000 injuries requiring emergency room care. Approximately 1,600 fires are ignited, resulting in the destruction of 200 million square feet of the building stock, the equivalent of 133,000 single-family homes. Fire contributes $87 billion in property and business interruption loss, out of the total $191 billion in economic loss, with most of the rest coming from shake-related building and content damage ($46 billion) and business interruption loss from water outages ($24 billion). Emergency response activities are depicted in detail, in an innovative grid showing activities versus time, a new format introduced in this study.

Expected seismic shaking in Los Angeles reduced by San Andreas fault zone plasticity

“…However, our simulation results show that nonlinearity in the fault zone is important even for conservative values of cohesion (as in model 1), suggesting that current simulations based on a linear behavior of rocks are overpredicting the level of ground motion in the LAB during future large earthquakes on the southern SAF. This would have far‐reaching implications on earthquake emergency planning scenarios that are based on ground motions predicted with linear wave propagation models, such as the damage scenario of the 2008 Great California ShakeOut [e.g., Porter et al , ; Lynch et al , ; Wein et al , ; Wein and Rose , ; Muto and Krishnan , ].…”

Three‐Dimensional Basin and Fault Structure From a Detailed Seismic Velocity Model of Coachella Valley, Southern California

“…The Salton Trough (Figure ) contains active faults that make it a high earthquake hazard region in Southern California (Jennings & Bryant, ; Jones et al, ). One of the most significant threats facing this region is an overdue estimated Mw 7.2 to 8.1 earthquake rupture at the southeastern end of the San Andreas fault near the Salton Sea, with energy propagating northward through the Coachella Valley into the Los Angeles basin (Day & Roten, ; Fialko, ; Jones et al, ; Olsen et al, ; Porter et al, ; Rose et al, ). Damage from such an earthquake would result in a great loss of lives and infrastructure in Southern California.…”

Rapid Estimation of Damage to Tall Buildings Using Near Real-Time Earthquake and Archived Structural Simulations

“…Furthermore, high-rise buildings are structures in which large numbers of people work or live and, if vulnerable to long-period motion from earthquakes, may become concentrated scenes of injured and entrapped persons. For instance, in the ShakeOut scenario of 2008, a total of 1800 deaths were posited to occur in a hypothetical magnitude 7.8 earthquake on the San Andreas fault (Jones et al, 2008;Porter et al, 2011). Of these, 439 deaths were attributed to the collapse of five high-rise steel MF buildings alone, 900 deaths to fire following the earthquake, and the rest were attributed to low-rise structure collapse.…”