Nav: Home

Geophysics: A surprising, cascading earthquake

March 21, 2019

The Kaikoura earthquake in New Zealand in 2016 caused widespread damage. Ludwig-Maximilians-Universitaet (LMU) in Munich researchers have now dissected its mechanisms revealing surprising insights on earthquake physics with the aid of simulations carried out on the supercomputer SuperMUC.

The 2016 Kaikoura earthquake (magnitude 7.8) on the South Island of New Zealand is among the most intriguing and best-documented seismic events anywhere in the world - and one of the most complex. The earthquake exhibited a number of unusual features, and the underlying geophysical processes have since been the subject of controversy. LMU geophysicists Thomas Ulrich and Dr. Alice-Agnes Gabriel, in cooperation with researchers based at the Université Côte d'Azur in Valbonne and at Hong Kong Polytechnic University, have now simulated the course of the earthquake with an unprecedented degree of realism. Their model, which was run on the Bavarian Academy of Science's supercomputer SuperMUC at the Leibniz Computing Center (LRZ) in Munich, elucidates dynamic reasons for such uncommon multi-segment earthquake. This is an important step towards improving the accuracy of earthquake hazard assessments in other parts of the world. Their findings appear in the online journal Nature Communications.

According to the paper's authors the Kaikoura earthquake is the most complicated ever recorded and raises a number of important questions. One of its most striking features was that it resulted in the successive rupture of more than 20 segments of a fault network. "Looking at the pattern of surface faults affected by the quake, one finds large gaps of more than 15 km in between them. Up to now, analyses of seismic hazard have been based on the assumption that faults that are more than 5 km apart will not be broken in a single event," says Gabriel. A second unusual observation was that, although the earthquake began on land, it also resulted in the largest tsunami recorded in the region since 1947. This indicates that the subsurface ruptures ultimately triggered local displacements of the seafloor.

The insights provided by the simulations have now yielded a better understanding of the causes of the sequence of fault ruptures that characterized the earthquake. "This was made possible by the realistic nature of our model, which incorporates the essential geophysical characteristics of fault failure, and realistically reproduces how subsurface rocks fracture and generate seismic waves," says Gabriel. The model confirmed that the Kaikoura earthquake involved a complex cascade of fault ruptures, which propagated in a zig-zag fashion. Propagation velocities along the individual fault systems were not unusually slow, but the complex geometry of the fault network and delays at the transitions between fault segments led to a tortuous rupture path. While a large amount of tectonic forces accumulating over decades may seem intuitively required to steer an earthquake throughout such complex fault networks, the authors suggest that the required forcing was on the contrary quite weak. "The rupture of such a weakly loaded fault was boosted by very gradual slippage or creep below the faults, where the crust is more ductile and low levels of frictional resistance, promoted by the presence of fluids", Gabriel explains. "In addition, high rupture velocities generally result in the rapid dissipation of frictional resistance."

The researchers state that their model could contribute to improving estimates of earthquake hazard in certain areas. Current hazard assessments require careful mapping of the fault systems in the region concerned, and their susceptibility to rupture under seismic stress is then estimated. "Earthquake modeling is now becoming an important part of the rapid earthquake response toolset and for improving long-term building codes in earthquake prone areas by delivering physics-driven interpretations that can be integrated synergistically with established data-driven efforts", says the first author of the study, PhD student Thomas Ulrich.
-end-


Ludwig-Maximilians-Universität München

Related Earthquake Articles:

Earthquake symmetry
A recent study investigated around 100,000 localized seismic events to search for patterns in the data.
Crowdsourcing speeds up earthquake monitoring
Data produced by Internet users can help to speed up the detection of earthquakes.
Geophysics: A surprising, cascading earthquake
The Kaikoura earthquake in New Zealand in 2016 caused widespread damage.
How fluid viscosity affects earthquake intensity
A young researcher at EPFL has demonstrated that the viscosity of fluids present in faults has a direct effect on the intensity of earthquakes.
Earthquake in super slo-mo
A big earthquake occurred south of Istanbul in the summer of 2016, but it was so slow that nobody noticed.
A milestone for forecasting earthquake hazards
In a new study in Science Advances, researchers report that their physics-based model of California earthquake hazards replicated estimates from the state's leading statistical model.
Mw 5.4 Pohang earthquake tied to geothermal activity?
The Mw 5.4 Pohang earthquake that occurred near a geothermal site in South Korea last year was likely triggered by fluid injection at the geothermal plant, two separate reports conclude.
Seismologists introduce new measure of earthquake ruptures
A team of seismologists has developed a new measurement of seismic energy release that can be applied to large earthquakes.
Residual strain despite mega earthquake
On Christmas Day 2016, the earth trembled in southern Chile.
The losses that come after the earthquake: Devastating and costly
The study, titled, 'Losses Associated with Secondary Effects in Earthquakes,' published by Frontiers in Built Environmen, looks at the devastation resulting from secondary disasters, such as tsunamis, liquefaction of sediments, fires, landslides, and flooding that occurred during 100 key earthquakes that occurred from 1900 to the present.
More Earthquake News and Earthquake Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#543 Give a Nerd a Gift
Yup, you guessed it... it's Science for the People's annual holiday episode that helps you figure out what sciency books and gifts to get that special nerd on your list. Or maybe you're looking to build up your reading list for the holiday break and a geeky Christmas sweater to wear to an upcoming party. Returning are pop-science power-readers John Dupuis and Joanne Manaster to dish on the best science books they read this past year. And Rachelle Saunders and Bethany Brookshire squee in delight over some truly delightful science-themed non-book objects for those whose bookshelves are already full. Since...
Now Playing: Radiolab

An Announcement from Radiolab