Scientists recently found evidence of a phase that occurs two hours before an earthquake ruptures, which could give warnings plenty of time, a new study has published. science Revealing The evidence was collected by analysis of Global Positioning System (GPS) time series data from nearly 100 major earthquakes around the world.
“Earthquake nucleation often involves a precursor phase lasting hours, and if methods can be developed to measure it reliably, a precursory warning could be provided,” said Roland Bergman, professor of earth and planetary science at the University of California, Berkeley.
The ability to predict large earthquakes has so far been an elusive goal. Short-term earthquake forecasting—the ability to provide warnings minutes to months before an earthquake occurs—depends on a critical, observable geophysical precursor signal. Previous studies of several large earthquakes have suggested that a precursor phase of slow aseismic slip can be observed on faults preceding the main shock.
The relationship between these observations and seismic ruptures, however, is that they do not directly precede an event and occur intermittently without an earthquake. As a result, the existence of a clear precursor signal capable of predicting large earthquakes remains uncertain. Quentin Bletary and Jean-Mathieu Noquet from the University of Côte d’Azur in France presented a systematic global search for short-lived precursor faults before large earthquakes.
It is unclear whether such slow-slip accelerations are clearly associated with large earthquakes.
Roland Bergman, professor at the University of California, Berkeley
Using global high-rate GPS time series data from 3,026 geodetic stations around the world, Bletery and Noquet measured fault displacement two hours before the onset of 90 different magnitude 7 and above earthquakes. Statistical analysis of the data began approximately two hours before a subtle signal rupture that coincided with a period of exponential acceleration of fault slip near the hypocenter of the earthquake.
According to the authors, the findings suggest that many large earthquakes begin at an earlier stage of slip or that the observations represent the end of a longer and more difficult to measure process of precursor slip. Although the study offers evidence of a precursor signal that indicates large earthquakes, currently deployed seismic monitoring equipment lacks the coverage and precision needed to identify or monitor foreslips at the scale of individual earthquakes, Blettery and Noquet note.
“Although the results of Bletery and Nocquet certainly suggest that there is a precursory phase lasting hours, it is not clear whether such slow-slip accelerations are clearly associated with large earthquakes or whether they can be measured for individual events with enough precision to provide useful warning,” Bergman said.