Will Another Earthquake the Size of the 1906 Earthquake Happen Again

The 1989 Loma Prieta convulsion in California damaged many buildings in San Francisco. Credit:Roger Ressmeyer/Corbis/VCG/Getty

The earthquake begins at iv:eighteen p.m. every bit a violent shudder, and rips along the Hayward Error eastward of San Francisco, California. Past the fourth dimension the magnitude-7 event is over, buildings and roads throughout the region have collapsed, h2o pipes have shattered and fires rage. Eight hundred people are dead, tens of thousands have become homeless, and many who are yet in their homes volition go without running h2o for weeks to months.

Fortunately, this is only a hypothetical scenario — for now. The US Geological Survey (USGS) devised information technology to recall through how emergency officials, city managers and the public might respond to a big earthquake that could plausibly strike the region. The scenario, released on 18 Apr, draws on lessons that scientists have learned from a spate of recent natural disasters. It'southward the almost detailed simulation withal of how an urban area might fare after a convulseⁱ.

Notably, the exercise explores how businesses, such as those in nearby Silicon Valley, can make themselves more resilient in the face of disaster. The USGS calls the scenario HayWired considering a Hayward quake could disrupt Internet connectivity in the Bay Area. "This is a scientifically defensible story of the blazon of matter you lot should exist getting fix for," says Lucy Jones, a former USGS seismologist who at present heads the Dr. Lucy Jones Center for Scientific discipline and Society in Burbank, California.

HayWired follows a similar practise in southern California a decade ago. Spearheaded by Jones, the 'ShakeOut' scenario envisioned a magnitude-7.8 quake hitting the Los Angeles surface area. Information technology was the first try to ally California'due south known seismic risk with a detailed scenario that brought the danger home. "For years we had been talking almost the Big One, but we weren't actually existence specific about what nosotros had in mind," says Kenneth Hudnut, a geologist with the USGS in Pasadena, California, and a leader of the HayWired exercise.

The USGS chose the Hayward error this fourth dimension because it has a 33% probability of experiencing a convulse of magnitude 6.7 or greater in the next 25 years — the highest in the San Francisco Bay Area. Palaeoseismic studies show that the last nine earthquakes of this size on the Hayward have happened at roughly 150-year intervals. The most contempo was a magnitude-6.8 tremor in Oct 1868, 150 years ago.

Seismic surprises

Today the fault runs through homes, transportation lines and the University of California's Berkeley campus. Many buildings have been retrofitted to withstand stiff shaking — but many take not. An convulsion hasn't significantly damaged the Bay Area since 1989, when the magnitude-6.9 Hill Prieta quake struck on the San Andreas Fault south of San Francisco. It killed 63 people and caused billions of dollars in destruction.

HayWired draws lessons from recent quakes effectually the world. A magnitude-7.8 quake in Gorkha, Nepal, in 2015 triggered at least 25,000 landslides in steep terrain², then HayWired includes the possibility of landslides in the hills east of the bay. Then in that location is a magnitude-half-dozen quake that struck just north of San Francisco in 2014, in the southern Napa Valley.

The initial tremor acquired part of a geological error to slide by less than 10 centimetres — but over the following year, the footing slowly crept by at to the lowest degree another 30 centimetres³. The HayWired scenario acknowledges that residents and business owners might delay building repairs for months to continue new construction from being damaged, which would prolong the post-quake economical slump.

And the 2010–eleven sequence of quakes near Christchurch, New Zealand, underscored the threat posed by aftershocks⁴. The deadliest quake in the serial was a magnitude-6.2 event that happened five months afterwards the biggest stupor, only killed 185 people because it struck near the city heart at lunchtime on a workday. The quakes "really emphasized to us how an earthquake is not simply a one-off effect to plan for and respond to", says Sally Potter, a hazard and risk management researcher at GNS Science in Wellington, New Zealand.

Edifice resilience

Because of the Christchurch feel, the HayWired exercise simulates how two years of aftershocks would affect the Bay Area. "In some cases, the shaking is stronger from the aftershock than from the main shock," says Anne Wein, an operations research analyst with the USGS in Menlo Park, California and a leader of the HayWired project.

HayWired focuses on getting businesses back up and operating. The scenario suggests that one in 4 buildings in the region volition be uninhabitable for months after a large convulse — only that people are willing to pay more to meet stricter building regulations to continue structures functional. California's state assembly is currently considering seismic-safety legislation that would require buildings to be safe to utilise immediately after a convulse.

"It's not merely making certain my employees don't get crushed," says Jones. "It's how do I start up business afterward?"

References

1. Detweiler, S. T. & Wein, A. Thou. (eds) USGS Scientific Investigations Report 2017-5013-A-H (2017).

2. Roback, Yard. et al. Geomorphology 301, 121-138 (2018).

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3. Lienkaemper, J. J., DeLong, S. B., Domrose, C. J. & Rosa, C. M. Seismol. Res. Lett. 87, 609-619 (2016).

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4. Potter, S. H., Becker, J. S., Johnston, D. M. & Rossiter, K. P. Int. J. Disaster Hazard Reduction 14, half-dozen-xiv (2015).

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Source: https://www.nature.com/articles/d41586-018-04489-3

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