Large Earthquakes Show Fault Movement on GPS Data 2 Hours Prior Seismic Rupture

GPS data reveals that, particularly for large earthquakes, fault movement occurs two hours before seismic rupture.

Previous Attempts at Earthquake Prediction

Several decades ago, small earthquakes and odd behavior from animals led to the establishment of an earthquake forecast in China. When the main earthquake did occur and caused widespread havoc, many people decided to sleep outside of their houses and were therefore spared.

Nevertheless, it is rare for such seismic activity to be succeeded by a notable earthquake, and unfortunately, the majority of earthquakes occur without any precursor indicators. Shockingly, the subsequent major earthquake in China claimed thousands of lives without any prior warnings, as per the USGS data.

GPS Data Shows Fault Movement

Evidence for a precursory phase of fault slip, which happens around two hours before seismic rupture, has been found through examination of Global Positioning System (GPS) time-series data from almost 100 significant earthquakes worldwide.

According to Roland Bürgmann, a precursor warning could be given if it is established that earthquake nucleation frequently entails an hours-long precursory phase and the tools are created to accurately assess it.

Short-term Earthquake Prediction

A distinct and detectable geophysical precursor signal is necessary for the short-term prediction of earthquakes, which involves giving a warning that comes minutes to months before a quake. Retrospective investigations in the past have suggested that a slow aseismic slide, acting as a potential forerunner, can be found in faults before the major shock. The relationship between these data and seismic ruptures is still not obvious, though.

This ambiguity results from the fact that these observations frequently take place without an accompanying earthquake and do not directly precede an occurrence, casting doubt on the possibility of an exact precursory indicator for predicting significant earthquakes.

Fault Movement 2 Hours Before Earthquake

Quentin Bletery worked with Jean-Mathieu Nocquet to describe a systematic global search for brief precursory fault slides before significant earthquakes in this study. Bletery and Noquet evaluated fault displacement for a maximum of two hours preceding 90 different earthquakes of magnitude 7 or higher using global high-rate GPS time-series data coming from 3,026 geodetic sites around the world.

When this data were statistically analyzed, a faint signal emerged that coincided with a time frame of the exponential increase of fault slide close to the earthquake's hypocenter that began about two hours before the fault rupture.

The authors conclude that either the data are the end result of a longer and more difficult-to-assess process of precursory slip, or that many major earthquakes begin with a precursory phase of slide.

Today's earthquake monitoring systems do not have the coverage or precision necessary to identify or keep track of precursory slip at the degree of individual earthquakes, warn Bletery and Noquet, despite the fact that they show indications of a precursory signal before major earthquakes.

It is unclear whether such slow-slip accelerations are specifically linked to large earthquakes or if the earthquakes could ever be determined for individual events with the precision needed to provide a reliable warning, according to Bürgmann, even though the results of the study suggest that there may be an hours-long precursory phase, SciTech Daily reports.

The study by Bletery and Nocquet was recently published in the journal Science.