A systematic global analysis of GPS time series data from nearly 100 major earthquakes indicates the presence of a fault slip prephase that occurred approximately two hours before the seismic rupture.

An analysis of time-series data from the Global Positioning System (GPS) around 100 severe earthquakes around the world found evidence of an earlier stage of fault slip occurring about two hours before the seismic rupture.

From a related perspective, Roland Bürgmann writes: “Forerunner warnings can be given if it can be verified that the onset of an earthquake usually involves an antecedent phase of many hours, and if tools can be developed to measure it reliably.”

Trying to predict strong earthquakes is a long-standing but challenging goal.

The problem of short-term forecasting of earthquakes

Short-term earthquake prediction, which involves giving a warning minutes or months before an earthquake, depends on the presence of a clear and discernible geophysical messenger signal. Previous retrospective studies have suggested that slow seismic slip on faults may occur prior to the main shock, a possible precursor. However, the relationship between these observations and seismic refractions remains unclear. This uncertainty arises because these observations do not precede the event and often occur without a subsequent earthquake, leaving an accurate signal of progression in existence for predicting the major earthquakes in question.

General search for previous errors

In this study, Quentin Blathery and Jean-Mathieu Nocke present a comprehensive global search for short-term pre-slip on faults before major earthquakes. Using a global high-speed time series GPS data from 3,026 geodetic stations around the world, Bleteri and Nocke estimated fault displacement two hours before 90 different earthquakes of magnitude 7 or greater. Statistical analysis of these data revealed a subtle signal consistent with the exponential acceleration period of the fault slip near the earthquake focal point, which began approximately two hours before the rupture.

Importance and limitations of the study

According to the authors, these findings suggest that many powerful earthquakes begin with a pre-slip phase or that the observations may represent the final part of a longer and more difficult-to-measure pre-slip phase. Blatheri and Nocke warn that although they provide evidence of a foreshock preceded by major earthquakes, current earthquake monitoring tools lack the coverage and sensitivity necessary to detect or monitor fore-slip at the scale of individual earthquakes.

Bürgmann writes: “Although Bleteri and Nocke’s results suggest that there may indeed be a multi-hour preliminary phase, it is unclear whether such slow-slip accelerations are clearly associated with strong earthquakes or whether they can be measured with the necessary precision to provide a useful warning for individual events.” Source