Scientists are about to test a devastating hypothesis: 2018 will suffer a lot of big earthquakes

Every so often, the Earth’s rotation slows by a few milliseconds per day. This is inconsequential to the average human, and causes only mild annoyance to the people whose job it is to measure Earth’s rotation with great precision.

That may be about to change, if the hypothesis set out by two geologists proves true. In a study published in Geophysical Research Letters earlier this year, Roger Bilham of the University of Colorado and Rebecca Bendick of the University of Montana predict that, because of Earth’s slowing rotation, the world will see a significant spike in large earthquakes in 2018.

To make this prediction, Bilham and Bendick studied every earthquake since 1900 that recorded more than 7.0 on the moment magnitude scale. They found that approximately every 32 years, there is an uptick in these large quakes. The only factor that strongly correlates is a slight slowing of the Earth’s rotation in a five-year period before the uptick.

“Of course that seems sort of crazy,” Bendick told Science. But think through it a little and it might not seem so outlandish. The Earth’s rotation is known to go through regular decades-long periods in which it slows down and speeds up. Even seasonal changes, like a strong El Niño, can affect the planet’s rotation.

But to have the kind of effect that would produce more severe earthquakes, we have to look deeper. Starting from its very center, the planet is made of a solid iron and nickel “inner core,” liquid iron and nickel “outer core,” a thick liquid mantle, and finally a thin solid crust. Earthquakes occur on the crust, but the crust floats on the mantle.

Though Bilham and Bendick don’t know for sure, they believe that every so often the Earth’s mantle might stick a little more to the crust. That could change how the liquid outer core flows. And because it’s all metal down there, the change in flow will affect planet’s magnetic field, which would ever so slightly affect the Earth’s rotation and thus change the length of the day by milliseconds. The Earth’s rotation has been slowing down for the past four years.

“The inference is clear,” Bilham told the Guardian. “Next year we should see a significant increase in numbers of severe earthquakes.” Instead of an average of about 15-20 large earthquakes, we might see 25 or 30 in 2018.

Bilham can’t tell with any certainty where these might take place. Many large earthquakes occur in places where they don’t affect human life, but in the wrong spot they can wreak havoc. As Quartz reported previously:

In an ill-prepared country like Haiti, a magnitude 7.0 earthquake in 2010 killed more than 100,000 people. In Japan, with much better buildings, a magnitude 9.0 quake (which releases about 1,000 times more energy than a 7.0) in 2011 killed some 18,000 people.

So, can we predict earthquakes? It’s a question that vexes seismologists, not because it is unreasonable, but because scientists have tried many times and always ended in failure. Even after many advances in seismology, as Richard Luckett of the British Geological Survey puts it, “when an earthquake occurs is essentially a random event.” Rightfully, that hasn’t stopped people from trying.

Alert raised for Iceland’s Öræfajökull volcano, last eruption was in 1728

New satellite images of Öræfajökull volcano shows that a new ice-cauldron has formed within the caldera in the last week. Pilot flying over the area took pictures of the cauldron today and sent them to the Icelandic Meteorological Office. The cauldron is about 1 km in diameter and it reflects a recent increase in geothermal activity within the caldera.

It seems that geothermal water has been slowly released from underneath the cauldron to the glacial river of the Kvíárjökull outlet-glacier (SE flank of Öræfajökull volcano). Associated with this water release sulphur smell has been reported nearby Kvíárjökull since last week. Most of the water has probably already been released. An increase in the seismic activity has been recorded for the last few months, but for the past days it has been low. This data indicates increased activity of the volcano which has not erupted since 1727. Currently there are no signs of an imminent eruption.

The Icelandic Coast Guard will fly over the area with scientists tomorrow to collect additional data and samples. The Icelandic Meteorological Office has increased the surveillance of the area and is monitoring the volcano closely in collaboration with scientists from the University of Iceland and the Icelandic Civil Protection Authorities.

The Icelandic Meteorological Office has in light of this elevated activity raised the aviation color code for Öræfajökull to yellow.

New insights into the 2004 Sumatra megathrust earthquake

An illustration of the so-called “subduction zone” between tectonic plates during the Sumatra earthquake, in which the ocean plate moved below the continental plate. (Image: Gabriel / Bader)

Scientists in Munich have completed the first detailed simulation of the Sumatra earthquake that triggered a devastating tsunami on Christmas 2004. The results of the largest-ever rupture dynamics simulation of an earthquake offer new insights into the underlying geophysical processes. It was performed on the SuperMUC supercomputer at the Leibniz Supercomputing Center (LRZ) of the Bavarian Academy of Sciences in Munich. The analysis could help with the development of more reliable early warning systems.

The Christmas 2004 Sumatra-Andaman earthquake was one of the most powerful and destructive seismic events in history. It triggered a series of tsunamis, killing at least 230,000 people. The exact sequence of events involved in the earthquake continues to raise many questions.

A deeper understanding of the geophysical processes involved is now closer at hand, thanks to a multi-physics simulation performed by a team of geophysicists, computer scientists and mathematicians from the Technical University of Munich (TUM) and the Ludwig-Maximilians-Universität (LMU) on the Super-MUC supercomputer at the Leibniz Supercomputing Center (LRZ).

PRECISE FORECASTING PRACTICALLY IMPOSSIBLE

In subduction zones – locations where tectonics plates meet at seams in the Earth’s crust, with one plate moving below the other – earthquakes occur at regular intervals. However, it is not yet precisely known under what conditions such “subduction earthquakes” can cause tsunamis, or how big such tsunamis will be.

Earthquakes are highly complex physical processes. In contrast to the mechanical processes occurring at the rupture front, which happen on a scale of a few meters at most, the entire Earth’s surface rises and falls over an area of hundreds of kilometers. During the Sumatra earthquake, the tear in Earth’s crust extended over more than 1,500 km (the approximate distance from Munich to Helsinki or Los Angeles to Seattle) – the longest rupturing fault length ever seen. Within 10 minutes, the seafloor was vertically displaced by the earthquake by as much as 10 meters.

SIMULATION WITH OVER 100 BILLION DEGREES OF FREEDOM

To simulate the entire earthquake, the scientists covered the area extending from India to Thailand by a three-dimensional mesh with over 200 million elements and more than 100 billion degrees of freedom.

The size of the elements varied according to the required resolution: A much finer mesh was used along the fault, to resolve the complex frictional processes, and on the surface, to take into account the topographical features and the relatively low-velocity seismic waves found there. In areas with little complexity and fast waves, a coarser mesh was applied.

To perform the seismic wave propagation calculations, more than three million time steps had to be computed on the smallest elements. As input data, the team used all available information on the geological structure of the subduction zone and the seafloor initial conditions as well as laboratory experiments on rock fracture behavior.

In addition to the large so-called megathrust plate boundary, the scientists considered three smaller splay faults, or branching faults, suspected of having strongly impacted the tsunami-triggering deformation of the ocean floor.

ALMOST 50 TRILLION OPERATIONS

“To make it possible to finish the simulation on SuperMUC within a reasonable period of time, it ultimately took five years of preparations to optimize our SeisSolearthquake simulation software. Just two years ago, the computing time for the simulation would have been 15 times longer,” explains Michael Bader, a professor of informatics at TUM.

All of the algorithmic components, from data input and output and the numerical algorithms to solve the physical equations through to the parallel implementation on thousands of multicore processors, had to be optimized for the SuperMUC.

The Sumatra simulation still took almost 14 hours on all 86,016 cores of the SuperMUC, which performed nearly 50 trillion operations (almost 1015 operations per second, or around 1 petaflop/s – one third of the theoretical maximum computing performance).

LARGEST AND LONGEST EARTHQUAKE SIMULATION EVER PERFORMED

“We successfully completed the largest earthquake simulation of this kind ever seen,” says the LMU geophysicist Dr. Alice-Agnes Gabriel. “With a duration of around eight minutes, it is also the longest. On top of that, it was the first-ever physics-based scenario for a real subduction rupture process. With the simultaneous calculation of the complicated fracture of several fault segments and the subsurface propagation of seismic waves, we gained exciting insights into the geophysical processes of the earthquake.”

In particular, says Dr.Gabriel, “The splay faults, which can be imagined as pop-up fractures alongside the known subduction trench, led to long-period, abrupt vertical displacements of the seafloor, and thus to an increased tsunami risk. At present, this capability of incorporating such realistic geometries into physical earthquake models is unique worldwide.”

The project was funded by the Volkswagen Foundation (Project ASCETE), Intel (as part of an Intel Parallel Computing Center) and the Leibniz Supercomputing Center of the Bavarian Academy of Sciences.

PUBLICATION:

“Extreme scale multi-physics simulations of the tsunamigenic 2004 sumatra megathrust earthquake” / doi>10.1145/3126908.3126948 will be published at the SC17 Conference in Denver, Colorado (USA), November 12-17, 2017.