EarthquakesSeismologists deploy after a quake to learn more, so we can prepare for the next one
The simple truth about great earthquakes, and the miserable cascade of events they often trigger, is this: if an earthquake has affected a region, recently or in historical records, then future earthquakes in that region are inevitable. Globally, we need a program of identification and characterization of potentially hazardous faults in urban areas. From those studies, site-specific expected seismic shaking maps can be developed and construction codes and engineering design specifications for infrastructure enacted, mitigating hazard to new and future construction. Then urban political leaders and civil defense agencies must collaborate to lead local populations in an open and honest dialog to identify both irreplaceable cultural heritage, and also infrastructure that must survive natural disasters intact in order to prevent an earthquake from triggering a series of consequent catastrophes — fires, water, and food shortages and disease outbreaks. These structures should be retrofitted to survive the predicted shaking from the maximum expected magnitude earthquake for the given area. A number of different mechanisms to pay for this costly preventive engineering are almost certainly needed, tailored to local conditions.
The past is never dead. It’s not even past. – William Faulkner
When disasters like the Nepal earthquake strike, seemingly out of the blue, one can’t help but feel anguish at the mismatch between the capacity of human memory and the tenacity of denial. The simple truth about great earthquakes, and the miserable cascade of events they often trigger, is this: if an earthquake has affected a region, recently or in historical records, then future earthquakes in that region are inevitable. But, if no damaging earthquake has happened in recent memory, it’s easy to ignore the need to prepare for a future event of uncertain magnitude and proximity. The earthquake cycle is long relative to the terms of a city council, a state legislature, and even a national government.
As a practicing seismologist, the political questions implicit in a discussion of how much risk a society is prepared to assume relative to the costs of mitigation are largely beyond my influence. On the other hand, seismologists like me can help address the question of where earthquakes have occurred in the past — and where they will occur again in the future.
We can estimate how large a magnitude earthquake can be expected in a given region. We can determine how different substrates — soils, sand, fill, bedrock — will affect ground shaking, and we can map the distribution of these foundational materials on a building-by-building scale, if necessary. We can assess the propensity for slope failure, which leads to landslides. And, for some regions, we can come up with ballpark estimates of the average time between large-magnitude earthquakes.
Even after a major quake, there’s much seismologists can learn that can hopefully help people prepare for the next one.
What do we want to know?
Scientists and policymakers ideally want to forecast the time, place, and magnitude of a future earthquake. Knowing that information well in advance, we could issue a region-specific targeted alert, complete with estimates of expected shaking. Such knowledge would allow for the maximum safeguarding of populace and infrastructure. Perfect forecasting would also mean no disastrous failures-to-predict and no false alarms.
So what can seismologists do to get closer to this goal?
