An earthquake can cause a lot of human lives. Precisely predicting the location, size and date of the next major earthquake is, therefore, a crucial research issue in the race to develop reliable warning devices. The United States National Research Council, Panel on Earthquake Prediction of the Committee on Seismology, suggested the following definition: “An earthquake prediction must specify the expected magnitude range, the geographical area within which it will occur, and the time interval within which it will happen with sufficient precision so that the ultimate success or failure of the prediction can readily be judged. Only by careful recording and analysis of failures as well as successes can the eventual success of the total effort be evaluated and future directions charted. Moreover, scientists should also assign a confidence level to each prediction.”
For a long time, seismological and geophysical studies have focused on the identification of “precursor” signs which consisted in detecting, in the vicinity of the seismic source, the abnormal phenomena preceding the earthquake: swarms of micro-earthquakes, deformations of the soil, disturbance of the aquifers, the electromagnetic fields or the behavior of the animals. But the demonstrations which presented after the fact, these “precursors” never made it possible to conceive reliable, reproducible and generalizable models, nor to understand the mechanisms at the origin of these phenomena. Many scientists associate these precursors with mere coincidences.
In the absence of predictions, many advances have been made in the field of forecasting, and research is now organized around three main axes:
The first is to predict, region by region, the magnitude of the ground movements that could be generated by a fault, in the event that it gives way. The monitoring of large faults by seismometers makes it possible to describe, from a statistical point of view, its rupture process, i.e., the amplitude and the frequency of the vibrations that it could generate by yielding. For the exposed region, the various scientific data collected are then integrated into a seismic risk calculation chain, which associates, upstream, the probability of breaking a fault, and downstream, the consequences relating to goods and people.
The second is to identify faults with a near break point. This type of threshold is evaluated from a historical study of earthquakes (search in the archives of all the earthquakes of a region; search for paleoseismic activity in the geological layers). This, when combined with geodesic measurements, make it possible to estimate the speed of loading of a fault, that is to say, the time interval spacing two breaks (two earthquakes) on the same segment of the fault. Thus, within a few decades, several major destructive earthquakes, the “big ones”, are predicted in California, Japan, Chile, Turkey or Greece.
Current models can predict where? At what magnitude? But currently, no one is able to answer the crucial answer precisely when? However, recent discoveries around anomalies associated with crustal deformations and fault activity are showing encouraging results. They have highlighted the existence of very low-amplitude rumblings called ” tectonic tremor “, related to the crunching of the deep part of the slow transient glide faults, and try to decrypt the recordings to deduce the probabilities of triggering the seismic rupture.
One of the leading seismologists in the world right now is Giuliano Panza. Panza has taught seismology in many reputable institutions and he is an Emeritus Honorary Professor at the China Earthquake Administration. Giuliano Panza is a renowned seismologist known for his expertise in elastic wave propagation and the study of the interior structure of the earth. Panza, in collaboration with Academician Keilis-Borok (Russia) developed a framework of Abdus Salam International Centre for Theoretical Physics in Trieste, Italy dedicated to the genesis and intermediate-term middle-range prediction of earthquakes that attracted young seismologists from Asia, South America, and Africa. Worldwide the performance of intermediate-term middle-range earthquake prediction algorithms reaches a significance level above 99%.