A large earthquake on one fault can trigger large aftershocks on separate faults within just a few minutes, scientists have found. The town of Pescara del Tronto was one of the worst hit with buildings flattened (pictured) by the magnitude 6.2 earthquake
A large earthquake on one fault can trigger large aftershocks on separate faults within just a few minutes, scientists have found. The town of Pescara del Tronto was one of the worst hit with buildings flattened (pictured) by the magnitude 6.2 earthquake that occurred last month
It is well known that earthquakes can cause widespread destruction to buildings and settlements close to the fault lines they occur on.

But according to a new study, the damage can be spread far further by triggering a tidal wave of aftershocks on other faults elsewhere.

A large earthquake on one fault can trigger large aftershocks on separate faults within just a few seconds, scientists discovered.

Scientists at Scripps Institution of Oceanography at the University of California San Diego discovered previously unidentified aftershocks that happened within minutes of big earthquakes.

The discovery is important for the safety of earthquake-prone regions like California - where ruptures on complex fault systems like the San Andreas fault may lead to mega-earthquakes.

In the study, published in the journal Science, geophysicist Professor Peter Shearer and graduate student Wenyuan Fan discovered 48 previously unidentified large aftershocks that occurred between 2004 and 2015.

In one instance along the Sundra arc subduction zone, where the magnitude 9 Sumatra-Andaman mega-earthquake occurred off the coast of Indonesia in 2004 (aftermath pictured), a magnitude 7 quake triggered two large aftershocks over 124 miles (200 kilometre
In one instance along the Sundra arc subduction zone, where the magnitude 9 Sumatra-Andaman mega-earthquake occurred off the coast of Indonesia in 2004 (aftermath pictured), a magnitude 7 quake triggered two large aftershocks over 124 miles (200 kilometres) away

These all occurred within seconds to minutes after magnitude 7 to 8 earthquakes on faults adjacent to the mainshock ruptures.

'The results are particularly important because of their seismic hazard implications for complex fault systems, like California,' said Fan, the lead author of the study.

'By studying this type of triggering, we might be able to forecast hosting faults for large earthquakes.'

In one instance along the Sundra arc subduction zone, where the magnitude 9 Sumatra-Andaman mega-earthquake occurred off the coast of Indonesia in 2004, a magnitude 7 quake triggered two large aftershocks over 124 miles (200 kilometres) away.

These aftershocks miles away reveal that stress can be transferred almost immediately by the seismic waves from one fault passing to another within the earthquake fault system.

Large earthquakes often cause aftershock sequences that can last for months.

Scientists generally believe that most aftershocks are triggered by stress changes caused by the permanent movement of the fault during the main seismic event, and mainly occur near the mainshock rupture where these stress changes are largest.

The new findings show that large early aftershocks can also be triggered by seismic wave transients, where the locations of the main quake and the aftershock may not be directly connected.

'Multiple fault system interactions are not fully considered in seismic hazard analyses, and this study might motivate future modeling efforts to account for these effects,' said Professor Shearer.
WHAT THE STUDY FOUND

A large earthquake on one fault can trigger large aftershocks on separate faults within just a few minutes, scientists have discovered.

The researchers discovered 48 previously unidentified large aftershocks that occurred between 2004 and 2015.

These all occurred within seconds to minutes after magnitude 7 to 8 earthquakes on faults adjacent to the mainshock ruptures.

The discovery is important for the safety of earthquake-prone regions like California - where ruptures on complex fault systems like the San Andreas fault may lead to mega-earthquakes.