The atmosphere is tense on the Indonesian island of Lombok. Over the last six weeks the island has been shaken by four serious earthquakes, resulting in more than 500 deaths and displacing several hundred thousand people. The question is, are there any more big quakes to come?
Richard Walters, a geophysicist at Durham University, sees eerie similarities between Lombok and the earthquake sequence that devastated central Italy in 2016. More than 300 people died in Italy’s Apennine mountains between 24 August and 30 October 2016, when the region suffered a series of three earthquakes, each larger than magnitude 6.
By analysing the timing of the quakes and the arrangement of faults along this mountain spine, Walters and his colleagues have shown that smaller cross-cutting faults acted as barriers, forcing the earthquakes to occur as a sequence rather than in one single, massive earthquake. “The pattern of small aftershocks suggests that each subsequent quake is triggered by fluids diffusing through the network of minor faults,” said Walters, whose findings have been published in Earth and Planetary Science Letters.
Lombok has similar cross-cutting faults, which may also be controlling the size of earthquakes in the Indonesian sequence. Given these similarities, investigating the migration of aftershocks might give valuable clues as to how the sequence will progress.