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2016 Ecuador tsunami and tremor data could predict future earthquake impact, analysis suggests


New research led by Brunel University London has revealed the potential threat of a large earthquake and tsunami off the shore of Ecuador and Colombia, to the north of last year’s major tremor.

While modelling the Ecuador earthquake of April 2016 - which claimed the lives of 660 people - Brunel civil engineering lecturer Dr Mohammad Heidarzadeh and colleagues in Tokyo observed its similarity to a 1942 earthquake.

The 2016 event was the largest damaging earthquake to hit the area in decades. It occurred in the same location as the 1942 event and both reached 7.8 on the moment magnitude scale (7.8 MW). The aftershock distribution of 2016 also covered the same rupture zone as 1942.

Hundreds have died along the Ecuador-Columbia coast as a result of three large megathrust tsunamigenic earthquakes (ruptures triggering tsunamis) in 1942, 1958 and 1979, rupturing in a consecutive order from south to north.

Writing in Geophysical Research Letters in March this year, the research team suggest that this sequence of triple ruptures could potentially repeat in the same way, putting the area to the north of the 2016 earthquake subject to potential large risks of earthquakes and tsunamis.

The 2016 earthquake was the result of the Nazca plate moving beneath the South American plate at a rate of 2.5 to 4.6cm a year off the shore of Ecuador-Columbia.

While the resulting tsunami was not as deadly or destructive as the tsunami of 1942, data collected on it provided valuable information to study the source of the earthquake.

The researchers conclude from analysis of tsunami and teleseismic data (measurements far from the earthquake) that the northward unilateral stress transfer from this large earthquake could possibly trigger future large earthquakes to the north of the 2016 epicentre in a way similar to the northward migrations of the 1942, 1958 and 1979 epicentres.

Dr Heidarzadeh comments: “Although rupture patterns along subduction plate boundaries are far from predictable, unilateral stress transfer has been observed in other subduction zones, for example, southward stress transfer from the 2004 Sumatra-Andaman 9.2 MW earthquake to the 2005 Nias 8.7 MW event and then to the 2007 Bengkulu 8.4 MW quake.”

“In recent years it has been observed that tsunami observations contain valuable information about earthquake sources, so we have used a combination of both teleseismic and tsunami observations to obtain source models.”

The joint use of teleseismic and tsunami observations in this study provides an accurate evaluation of the earthquake source which is critical in assessing future earthquake/tsunami hazards.    

Dr Heidazadeh’s body of research focuses largely on the interaction of coastal structures and extreme geo-environmental coastal hazards, with recent studies focusing on the coasts of Italy, Pakistan-Iran, Chile, Solomon Islands, and British Columbia, Canada.

Geologists and seismologists have long been able to work out the approximate risk of future earthquakes, based on historical patterns and instrumental data. But Dr Heidazadeh’s research continues to explore and develop new modelling methods, aiming for greater accuracy in predicting damage from earthquakes and tsunamis - influencing the development of coastal structures and reducing future loss of life.

Fault size and depth extent of the Ecuador earthquake of 16 April 2016 from teleseismic and tsunami data’ by Mohammad Heidarzadeh, Satoko Murotani, Kenji Satake, Tomohiro Takagawa and Tatsuhiko Saito is published in Geophysical Research Letters.

(Image: A collapsed overpass in Guayaquil - AgenciaAndes - used via CC)