The study revolves around this question: is it unlikely that one major earthquake will follow directly on the heels of a big quake, or are other major earthquakes equally likely to occur any time after a major quake" Hazard estimates for a seismic zone depend on which scenario seismologists choose to plug into their hazard calculations.
The present hazard maps for New Madrid and Charleston use the second assumption. However when seismologist Seth Stein of Northwestern University and Northwestern senior James Hebden chose the first scenario—that a quake is unlikely to occur right after another quake, but that the likelihood of a new quake increases over time—they found that the seismic hazard maps of the New Madrid and Charleston areas looked a lot less dire than current predictions for the regions.
Their “time-dependent” model suggests that the likelihood of another earthquake is relatively low for the first two-thirds of the predicted average interval between earthquakes, after which the likelihood of another quake begins to climb.
The New Madrid and Charleston zones are still in the early years of their earthquake cycle, so the hazard may not be as great as suggested by the prevailing “time-independent” models that assume another quake is equally likely to occur at any moment, according to the researchers.
Stein says the idea behind the study is not to dismiss the risk of a major earthquake in the two regions, but to shed light on the assumptions that go into making hazard maps, which ultimately affect a region’s building codes and other costly preparations.
“We want to know how well we can predict that shaking. If we overpredict, communities could be spending enormous amounts of money [on earthquake preparation] that they could be spending on other things,” Stein said. “We look at it as whether you’re going to spend money putting steel in your schools that might be better spent hiring teachers.”
“What we’re saying is that this may be nowhere as serious a problem as you’ve been told, and you don’t need to prepare in St. Louis the way we do in Los Angeles, because that may be doing more harm than good,” he added.
The desire to prepare is understandable, given the devastation caused by the last major earthquakes in the New Madrid zone in 1811 and 1812, and in Charleston in 1886. The 1811-1812 New Madrid earthquakes uprooted entire forests and changed the course of the Mississippi River. The Charleston earthquake killed more than 60 people and caused damage to nearly every structure in the city, traces of which can still be seen today.
To prepare for the potential dangers of similar severe quakes in the future, seismologists construct hazard maps, which predict the extent of earthquake shaking that has a certain probability of occurring in a geographical area. The hazard maps take into account the possible magnitude of the next earthquake, the likely ground shaking, the time window in which the next quake is likely to occur, and whether earthquakes are time-dependent or time-independent processes.
It’s an admittedly “squishy” calculation, Stein says, even in places like California’s San Andreas zone that have experienced many more earthquakes in recent years and have been monitored by a blanket of instruments.
Stein and his colleagues have tested each of these variables, from magnitude to timing, to explore which factors may have the greatest effect on hazard mapping for the central U.S.. But he says that the question of time-dependent or time-independent earthquakes is “the meatiest scientific question” among the mapping variables.
The question goes to the heart of how earthquakes work. For instance, most seismologists think there is a buildup of elastic strain in the earth before a quake occurs, and that the strain is relieved for a time by the quake. Under this scenario, a time-dependent model of earthquakes might make more sense to use in hazard maps. But it’s far from clear that the popular strain buildup model completely describes the physics of earthquakes, Stein says.
“It’s actually kind of embarrassing that we don’t know the answer to this,” Stein jokes. “But when you do this kind of thing, you want to have a healthy humility in the face of the complexities of nature.”
Nan Broadbent | EurekAlert!
Predicting unpredictability: Information theory offers new way to read ice cores
07.12.2016 | Santa Fe Institute
Sea ice hit record lows in November
07.12.2016 | University of Colorado at Boulder
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
07.12.2016 | Health and Medicine
07.12.2016 | Life Sciences
07.12.2016 | Health and Medicine