The fault slips that generate earthquakes release lots of stored energy, energy that reverberates violently across the planet's crust. But earthquakes also create new stresses.

New research suggests the accumulation of stress caused by historic earthquakes could explain why and where the next seismic event occurs.

In regions vulnerable to earthquakes, major seismic events seem to occur at random. But new findings -- published this week in the journal Nature Communications -- suggest the static stress stored on a fault plane prior to rupture, so-called Coulomb pre-stress, can help explain historic and modern earthquake patterns.

Until now, most models assume pre-stress is zero, but authors of the new study suggest such an assumption is flawed. The stress on a brittle fault plane is accumulated over centuries to millennia as a result of tectonic loading and a history of earthquakes. Through their analysis, scientists showed Coulomb pre-stress should not be ignored.

Researchers used written accounts of historic earthquake damage, modern seismic data and state-of-the-art modelling to show positive stress caused by a history of earthquakes is almost always present along faults prior to rupture.

"Earthquakes are caused by rock sliding past each other along fault lines which causes the forces and stress in the surrounding rocks to change after a big earthquake," Zoe Mildon, lecturer in earth sciences at the University of Plymouth, said in a news release. "It is often assumed that the nearest fault to a particular earthquake will be the next to rupture."

The latest study showed that is rarely the case. According to Mildon and her colleagues, current earthquake prediction models are over-reliant on Coulomb stress transfer theory, CST, which describes the transfer of stress to surrounding material in the wake of a seismic event.

The new study suggests cumulative stress, or historical stress, within fault systems is a better predictor of future earthquakes.

"Our model adds the stresses of lots of earthquakes together and shows that in the majority of cases fault lines are positively stressed when they rupture," Mildon said. "It is a step change in modelling CST and shows this is an ignored yet vital factor when trying to explain earthquake triggering."

Scientists arrived at their conclusions after studying the history of earthquakes in Italy's central Apennines region. When researchers tracked the location of earthquakes in the region over the last 700 years, they found 97 percent of the faults were wholly or partially stressed -- boasting a positive Coulomb pre-stress -- prior to rupture.

"Earthquakes are hugely destructive to both people and property, and the Holy Grail of earthquake science would be to predict where they are going to happen and when," Mildon said. "We are a very long way from that, and indeed it may never be possible to accurately predict the location, time and size of future earthquakes. Our research, however, could be a starting point in helping us develop better forecasts of which fault lines might be more susceptible based on previous tremors."

Powerful Indonesian quake felt in Australia
Jakarta (AFP) June 24, 2019 - A 7.3-magnitude earthquake struck remote eastern Indonesia on Monday, forcing people to flee office buildings as far away as the northern Australian city of Darwin, officials and reports said.

The deep and powerful earthquake sent shockwaves around the region, with people on the tourist island of Bali as well as in East Timor reporting feeling the tremor.

Indonesia was the epicentre of the Asian tsunami in 2004 that killed more than 170,000 people but the Pacific Tsunami Warning Center said Monday's quake was too deep to trigger a destructive wave.

Indonesia's disaster agency, which urged people to "stay calm", said the tremor was felt weakly in faraway Bali.

It hit at a depth of 208 kilometres (129 miles) south of Ambon island in the Banda Sea at 11:53 local time, according to the US Geological Survey (USGS).

There were no reports of casualties or any major damage.

"Wow, that was quite an impact for #Darwin, hope everyone is safe," the bureau of meteorology in Australia's Northern Territory said on Twitter.

People in Darwin's central business district fled buildings after the quake struck, the Australian Broadcasting Corporation reported.

The Southeast Asian archipelago of Indonesia, which is one of the most disaster-prone nations on Earth, lies to the north of Australia.

While the quake was too deep to spark a tsunami, its raw power jolted the region.

"The earthquake occurred at a depth of about 200 kilometres, and as the energy spreads upwards and outwards from the point at which it occurs, it will be felt in places as far away as Darwin," said Chris Elders, a quake expert at Australia's Curtin University.

Residents of Dili, the capital of East Timor, which lies southwest of the epicentre, were terrified as buildings shook.

"I was shocked. People were running around and screaming," Agida dos Santos told AFP.

"I saw the ground shaking -- it was really scary," added the woman, who was in her Dili home when the quake struck.

Earlier Monday, Indonesia's Papua province was hit by a 6.1-magnitude earthquake, about 240 kilometres (150 miles) west of the town of Abepura, at a relatively shallow depth of 21 kilometres, according to the USGS.

There were no immediate reports of casualties after that quake.

A shallower 6.3-magnitude tremor hit the area last week, but the damage was not extensive.

Indonesia experiences frequent seismic and volcanic activity due to its position on the Pacific "Ring of Fire", where tectonic plates collide.

Last year, a 7.5-magnitude quake and a subsequent tsunami in Palu on Sulawesi island killed more than 2,200 with a thousand more declared missing.

The massive quake that triggered the Asian Tsunami on December 26, 2004 struck in Aceh province and was measured at magnitude 9.1.

str-burs/pb/jah

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