Earthquake in Calabria, Unical professor Carbone speaks: “Complex system, impossible to predict”

John

By John

“The immediate response is a sequence of aftershocks, that is, after a major earthquake a series of earthquakes of lesser intensity begins in the same area, which follow one another at increasingly more distant intervals, until normal seismic activity is reached, most of which is imperceptible.” This was stated to AGI by the Physics professor atUniversity of Calabria, Vincenzo Carbone explaining what happened late Thursday evening when all of Calabria was shaken by a strong earthquake. “Calabria – explained Professor Carbone – is a land with a high seismicity, due to its location as a hinge between Africa and Europe, and between the Balkans and the Iberian parts. In the province of Cosenza alone there are at least 20 active main faults. An earthquake occurs because the Earth is an active planet. There is a convective process because the Earth’s core is hotter, and therefore energy is transported from the center of the Earth, which reaches the lithosphere creating stress that accumulates in the faults, and sometimes, due to a break at a certain depth, the stored energy is released. This is roughly the mechanism. The damage produced is generally inversely proportional, to some extent, to the depth of the hypocenter. In our case, fortunately, the earthquake was quite deep, 28 km according to INGV sources. And then we have certainly learned to build better. Earthquakes are inevitable, they are an integral part of the Earth system. Predicting where and when the next one will happen is not possible, nor do I think it will ever be possible in these terms, not because of our inability, but because of the complexity of the system. For the moment we can do nothing but monitoring and prevention. There are no physical models that allow us to predict earthquakes, except in a very general sense and without practical use, so monitoring allows us to accumulate data for statistical study. Prevention is obviously essential because we have to live with these natural processes, and therefore building resilience is necessary, with the methods of construction for example. A few years ago, with my research group, we were busy building physical models of a generic seismic event and trying to calculate the probability of occurrence in some very particular cases, for example in the presence of an accelerating sequence. The problem we have been dealing with in the last two years – added the Unical professor – is the observation, measurement and modeling of earthquakes from space. The shaking of the ground triggers a disturbance in the atmosphere that can propagate upwards and be detected as a disturbance of the magnetic field in the ionosphere by satellites in orbit. There are some Italian-Chinese satellites, with which we have been collaborating constantly for some years, that make this type of measurement, and others will be launched into orbit shortly. There is a very active collaboration underway on this issue. I am the scientific coordinator of a ministerial research project PRIN, which began this year and will continue for the next 3 years, which was evaluated with the maximum score by international reviewers in the Geophysics sector. The project aims to build physical models of this process of triggering and observation from above of earthquakes. The idea is twofold: 1) to do seismology from space, not through seismographs on the ground, but through satellites looking from the ionosphere; 2) with seismographs it has never been possible to find precursors of an earthquake. We want to see if, instead, looking from the ionosphere which is sensitive not only to physical disturbances (ground shaking), but also to electromagnetic disturbances, it is possible to observe some credible precursor. We do not yet know if the earthquake in Calabria produced the disturbance in the ionosphere, we will see in a few days, and if possible, we will see the Pietrapaola earthquake from space and, if it produced some signal, we will study it in detail. I believe this alternative way of looking at a seismic event could become, if not the future, at least an important integration of the usual seismic monitoring with ground-based seismographs. But certainly with much more potential. Having an alternative vision of the process, I believe, is essential to try to better understand the physical process of the earthquake and, above all, to look for the precursors, which would be the epochal turning point in seismology”.