before after
A picture of Amatrice before and after the earthquake struck

The earthquake that struck centre Italy few days ago reminded us, once again, of Nature’s power. Nevertheless, it also firmly reminds us that human beings have the possibility to limit the damages caused by natural disaster. An earthquake of 6.2 magnitude, cannot possibly cause such devastation we have witnessed these days. Back in 2009, a similar quake shook the Italian city of l’Aquila killing 308 people. Criticisms arose when it became clear that not only ancient buildings (characteristics of Italian landscape) meltdown, but also modern constructions were completely razed to the ground by the earthquake. On this regard, an Italian official of the Civil Protection Agency, Franco Barberi, stated: “in California, an earthquake like this one would not have killed a single person”.
After seven years, things have not changed in Italy. Corruption, bad policies undertaken by the State, unclear distribution of the available funding, are all factors that contributed to raise the death toll of this umpteenth Italian disaster. To fully show us that it is indeed possible to do something against these calamities, one has just to give a look at the village of Norcia. This little town is only 11 kilometres far from the earthquake’s epicentre, however, no major downfalls, and especially no deaths, were registered. “The re-building process saved the lives of many in the last decades”, confirmed the major of Norcia, Nicola Alemanno. What happened in Norcia represents a lesson for everyone. Building anti-seismic edifices secures the life of many.

Earthquakes, as other natural calamities, continue to scare and fascinate humanity. In ancient times, such catastrophes were seen as messages from the Gods asking for subjection and redemption. Luckily, modern science shed light on all these natural phenomena, and more effort is today ongoing to better understand how to react to these events and what to do for limiting damages to men and goods.

 Where scientific research on earthquakes stands and what’s next in this field and what should we do in case of an earthquake?

To answer these questions, Take it Science reached out to Prof. Aldo Zollo. Aldo is professor of Seismology at the department of Physics, University of Naples “Federico II”, and his ongoing research work focuses on studying earthquakes and volcanoes modelling and dynamics.

1) Professor Zollo, which kind of earthquake struck centre Italy and why was it so destructive despite a magnitude of 6.2?

Earthquake are related to fracture phenomena generally occurring at shallow crustal depth, e.g. 10-20 km beneath the Earth surface. The earthquake ruptures nucleate in a small region nearby the hypocentre but suddenly develop along internal faulting surfaces which can reach large or very large areal extents, depending on the magnitude of the earthquake and its released energy.

The August, 24 Amatrice earthquake originated along one of the numerous faults cutting the Central Apenninic belt, at shallow depth (<10 km), along a 20-25 km long segment, trending NNW-SSE between the towns of Norcia and Amatrice.

The proximity of the causative fault to urban settlements (less than 20 km) can be one major cause of the huge death toll and widespread damage, since the seismic wave amplitudes and high-frequency content are much greater at short epicentral distances. But extensive damage are also caused by the poor quality of constructions which could have resisted to the strong shaking produced by a M 6-6.5 earthquake if they were designed or retro-fitted according to anti-seismic construction rules.  

2) Why Italian territories are so earthquake-prone?

The Italian peninsula is among the highest seismic hazard areas of the Euro-Mediterranean region. Due to the convergent motion of African and Euro-Asia tecnonic plates Italy undergoes relatively high deformation rates (of the order of several millimeters per year). The related strain energy is accumulated along the fault systems in Apenninic chain, for very long time periods, and it can occasionally release to give rise to moderate or large earthquake ruptures, associated with event magnitudes of 6-7. More than 10000 earthquakes per year are currently recorded by the national seismic network operated by INGV, most of these events are so small that they are not perceived by populations.

3) Everybody knows that it is still impossible to predict beforehand when an earthquake will hit. Do you foresee any scientific advancement in the near future?

Earthquake prediction is the dream of any seismologist but we are actually very far from its realization. Predicting an earthquake, in the deterministic sense, means to anticipate the origin time, the place and the magnitude of the future earthquake. This would require on one hand, to have the complete understanding of the physical processes underlying the the preparation and nucleation phases of an earthquake rupture but also being capable to observe with an extremely dense sensor network the stress-strain field at depth in the region of the future unknown event. While enormous progresses have been made to simulate and control earthquake rupture in laboratories or by numerical modelling , science is not yet at the stage of having a reliable deterministic model to predict earthquakes.

The probabilistic , medium and long-term earthquake prediction, that seismologists denote as earthquake forecast, is instead feasible and actually applied at national and regional scale to produce hazard maps. The hazard map is built upon the seismic catalogue of an earthquake prone area, and includes geological and geodetic information. It represents the ground acceleration level which has a 10% probability to be exceeded in a given time span, typically 10 yrs. This map is indeed used in Italy by seismologists and earthquake engineers to classify the Italian territory in different hazard level zones and to set anti-seismic construction rules and criteria for each zone.

With the deployment of Early Warning systems, new data are being available about the very early signals emitted by earthquakes which corresponds to the initial phases of the earthquake rupture. New observations indicate that signal characteristics are different between small and large earthquakes at the very beginning of the earthquake rupture. If confirmed , this observation would imply that few tens of seconds of early recorded signals can provide the information about the size of the event and thus allow a prompt action to secure peoples in zones with high seismic risk.   Much work has to be done in the area of control engineering to link the seismological observation with the automatic actions to be done by specific servo-mechanisms during emergencies in order to mitigate the earthquake damages.

4) In what consists the “early warning”? Can it be useful?

Seismic early warning is a modern real-time, automatic method to issue an alert about a potential damaging earthquake before that large amplitude, destructive waves reach the target structure to protect. Once the earthquake occurs, the fastest P-waves can be rapidly detected and automatically processed at the sensor network deployed in the source area. Based on the automatic analysis of amplitude and frequency content of these early signal and Early warning System estimates the location and magnitude of the event and predicts the level of strong shaking at distant sites from the earthquake source.

Since the information travels at the light-speed while damaging seismic waves at few km per seconds withing the Earth crust, the alert message can reach sites to be protected several seconds or tens of seconds before the arrival of strong shaking waves.

5) How useful issuing an earthquake alert a few seconds or a few tens of seconds in advance, compared to the arrival of potentially destructive seismic waves?

To answer this question, one should analyze all the possible automatic or individual actions that can be undertaken in such a tight timeframe When at home, the street or in the workplace. In a report published on 2002 by J. Goltz, a specialist in Disaster Management and member of the Office of Emergency Governorship of California, he reviewed all the possible applications of Early Warning and seismic risk mitigation actions.
This analysis considered the sectors of Education, Health, the State and Local Agencies for the post-earthquake emergency, the transport services and networks for the supply of electricity and gas.
The report concludes that the Early Warning is feasible in California, after the implementation of a robust system of processing and transmission of data in real time, and the definition and pilot testing of a scientific protocol for validation and dissemination of the alert message to the potential users. The report is then provided with a list of possible actions following an early warning for each of the sectors concerned and the amount of good time. Among these, the automatic interruption of electricity / gas for the prevention of fires, interruption of operations in operating rooms, the arrest of hazardous materials transport in chemical industries or on building sites, the activation of semi-automatic systems for the protection of buildings, the air traffic control, road and rail, the activation of the emergency response by the fire department, a number of protective measures at home, in schools, in public buildings.

The Japanese experience of more than 10 years of operational Early Warning shows that not only automatic but also individual actions are feasible in a few seconds as the “drop, cover and hold” secure actions to be performed in schools by pupils after the ringing of an earthquake emergency siren triggered by an early warning system.

6) Which you think will be the next breakthrough in the field?

My present work field is the development of the next generation of earthquake early warning system. These should be capable to use the available time delays to trigger alerts and safety actions. I am therefore working at conceiving a new, physically-based real-time (RT) alert system operating in the earthquake source region, based on a “quake-shake forecast” system, acting at an extremely smaller time scale (seconds to tens of seconds). The idea is to interface it with a decision/control expert system, managing both the regional and local information and being capable to pilot user-specific individual/automatic actions to minimize losses to people and machinery and to maximize the site resilience following the event.

 

7) Lastly, a small off-topic: are volcanic eruptions so unpredictable as earthquakes?

Let’s start saying an obvious but effective statement: While the time and size of an eruption are unpredictable, its location is well determined at the volcano position as well as the extent of geographical area where the future eruption could have a devastating impact.

An eruption is caused by the rising of magma from mid-crustal or shallow crustal depths and it is generally preceded and accompanied by the manifestation of a number of geophysical and geochemical precursors, as the number, location and mechanisms of microearthquakes, ground uplift of in general the volcano deformation pattern, changes in fumerole gas composition and temperatures, gravity/magnetic anomalies, …

Volcanoes in Italy are densely instrumented and monitored by INGV with multi-parametric sensor networks linked in real or near-real time to the centralized control room, with a 24/7 operational monitoring service. It is therefore very unlikely that anomalies in the occurrence of precursory phenomena at volcano cannot be promptly detected and recognized as the starting of an unrest phenomenon. On the contrary the sensitivity of the monitoring network is actually so high that that the probability of false alarms triggered by the occurrence of anomalies which are not followed by an eruption is not negligible. How to deal with the occurrence of false alarms in a very high populated area nearby a volcano, such as Mt. Vesuvius or Campi Flegrei is really an intriguing and difficult task for the Department of Civil Protection.

Take it Science thanks Prof. Aldo Zollo for his great availability and for telling us what is going on in the fascinating field of earthquake research .

In conclusion, we really hope that Prof Zollo taught to all of us the most important lesson:

– Knowledge, behaviour and farsightedness can save many lives when it comes to natural disasters such earthquakes –

Davide Mangani

 

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