Archives par mot-clé : Earthquakes

‘Melting rock’ models predict mechanical origins of earthquakes

by Duke University, January 17, 2019 in ScienceDaily/Nature


Engineers at Duke University have devised a model that can predict the early mechanical behaviors and origins of an earthquake in multiple types of rock. The model provides new insights into unobservable phenomena that take place miles beneath the Earth’s surface under incredible pressures and temperatures, and could help researchers better predict earthquakes — or even, at least theoretically, attempt to stop them.

The results appear online on January 17 in the journal Nature Communications.

“Earthquakes originate along fault lines deep underground where extreme conditions can cause chemical reactions and phase transitions that affect the friction between rocks as they move against one another,” said Hadrien Rattez, a research scientist in civil and environmental engineering at Duke. “Our model is the first that can accurately reproduce how the amount of friction decreases as the speed of the rock slippage increases and all of these mechanical phenomena are unleashed.”

For three decades, researchers have built machines to simulate the conditions of a fault by pushing and twisting two discs of rock against one another. These experiments can reach pressures of up to 1450 pounds per square inch and speeds of one meter per second, which is the fastest underground rocks can travel. For a geological reference point, the Pacific tectonic plate moves at about 0.00000000073 meters per second.

Hadrien Rattez, Manolis Veveakis. Weak phases production and heat generation control fault friction during seismic slip. Nature Communications, 2020; 11 (1) DOI: 10.1038/s41467-019-14252-

Relation entre l’ activité sismique dans les océans et le réchauffement global (août 2019)

c/o Luc Trullemans,  août 2019 in PublicMétéo


Introduction

Une forte relation à été observée ces dernières années entre de l’activité sismique dans les océans et le récent réchauffement climatique  (CSARGW ,Correlation of Seismic Activity and Recent Global Warming) .

Cette corrélation entre de l’activité sismique océanique et le réchauffement climatique avait déjà été remarquée de 1979 à 2016 (CSARGW16) et vient d’être confirmée jusqu’en 2018.

Dans cette note, on démontre que  l’activité sismique dans les océans ( =>tremblements de terre de magnitude 4-6) provoque des flux géothermiques sous-marins et ont une relation importante avec les fluctuations de la température globale des océans (SST) et de la température globale de l’air (GT).

Ceci avance une nouvelle l’hypothèse selon laquelle l’activité sismique océanique pourrait être  un des paramètres  les plus importants dans la variation de la température globale.

 

 

Research into deadly 2016 Italian earthquakes could improve future seismic forecasts

by Durham University, Augsut23, 2018 in ScienceDaily


The timing and size of three deadly earthquakes that struck Italy in 2016 may have been pre-determined, according to new research that could improve future earthquake forecasts.

A joint British-Italian team of geologists and seismologists have shown that the clustering of the three quakes might have been caused by the arrangement of a cross-cutting network of underground faults.

The findings show that although all three earthquakes occurred on the same major fault, several smaller faults prevented a single massive earthquake from occurring instead and also acted as pathways for naturally occurring fluids that triggered later earthquakes.

Geologists detail likely site of San Andreas Fault’s next major quake

by Utah State University, June 26, 2018 in ScienceDaily


The discovery of the Durmid Ladder reveals the southern tip of the San Andreas Fault changes fairly gradually into the ladder-like Brawley Seismic zone. The structure trends northwest, extending from the well-known main trace of the San Andreas Fault along the Salton Sea’s northeastern shore, to the newly identified East Shoreline Fault Zone on the San Andreas’ opposite edge.

“We now have critical evidence about the possible nucleation site of the next major earthquake on the San Andreas Fault,” says Jänecke, professor in USU’s Department of Geology. “That possible nucleation site was thought to be a small area near Bombay Beach, California, but our work suggests there may be an additional, longer ‘fuse’ south of the Durmid Ladder within the 37-mile-long Brawley Seismic zone.” …

Evaluating active pressure management of induced earthquakes

by Seismological Society of America, May 17, 2018 in ScienceDaily


The experiments conducted by Lawrence Livermore National Laboratory researcher Kayla Kroll and her colleagues were prompted by a recent spike in induced earthquake activity related to oil and gas production in the U.S. and Canada. The rise in induced earthquakes has some scientists proposing changes in injection or production processes to reduce the fluid pressures that destabilize faults in these regions.

In their simulations, Kroll and colleagues “found that active management was most advantageous for wells that were closest to a fault. This scenario is most successful at reducing the total number of seismic events and also the maximum magnitude of those events,” Kroll said. In their simulations, a “close well” was one to four meters away from a fault (…)

Small earthquakes caused by migrating gasses in the underground

by GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre, May 1, 2018 in ScienceDaily


The metropolitan area of Istanbul with around 15 million inhabitants is considered to be particularly earthquake-prone. In order to be able to assess the risk correctly, researchers must decipher the processes underground. Below the Marmara Sea, an international research team detected earthquakes that were not directly caused by tectonic stresses but by rising natural gas.

Earth’s Rotation Is Mysteriously Slowing Down: Experts Predict Uptick In 2018 Earthquakes

by Tevor Nace, November 20, 2017 in WhoaScience


Scientists have found strong evidence that 2018 will see a big uptick in the number of large earthquakes globally. Earth’s rotation, as with many things, is cyclical, slowing down by a few milliseconds per day then speeding up again.

You and I will never notice this very slight variation in the rotational speed of Earth. However, we will certainly notice the result, an increase in the number of severe earthquakes.

Geophysicists are able to measure the rotational speed of Earth extremely precisely, calculating slight variations on the order of milliseconds. Now, scientists believe a slowdown of the Earth’s rotation is the link to an observed cyclical increase in earthquakes.