Nepal : an earthquake expected but not provided
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The area of Nepal that was hit by the 25 April 2015 magnitude 7.8 earthquake was known to geologists and seismologists for its seismic risk and, because of the extreme vulnerability of the edifices, it was and still is considered one of the regions at highest risk in the world.
The seismic activity in Nepal and surrounding areas is the result of the convergence between the Indian plate to the south, and the Eurasian plate to the north, which is the cause for the formation of the Himalayan mountain chain. The relative movement between the two plates amounts to about 5 cm per year (it is estimated that about 2 cm per year are accumulated along the southern margin of the mountain chain). This means that every century, a deformation of 2 m of relative displacement accumulates between the two plates. In the area affected by the 25 April earthquake, no strong earthquakes had occurred since centuries; for this reason the area around the capital Kathmandu was considered a seismic gap.
Figure 2 shows the seismic potential of the entire contact belt between the Indian and Eurasiatic plates (curved black line): the red and pink columns indicate for each section the quantity of displacement (in meters) that could occur during an earthquake. In the case of the zone hit by the 25 April 2015 earthquake, possible co-seismic movements of 4 to 10 meters were considered. The area immediately to the east of the recently stricken zone had been affected by a magnitude 8+ earthquake in 1934, which is why the corresponding column in Figure 2 shows an accumulation since then of "only" 1-2 m. The geological section (in the inset at upper right in Figure 2) shows how the Indian plate slides beneath the Eurasian plate, leading to the uplift of the Himalaya. The portion of the contact between the plates indicated as "locked" (dotted line in the figure) has remained blocked "for centuries" in the inter-seismic period, and moves suddenly when the resistance of the fault is exceeded: in that moment, an earthquake resets, temporarily, the geological equilibrium. For further in-depth reading visit the CIRES web site: http://cires1.colorado.edu/~bilham/HimSeismicGaps.html
The Nepal earthquake is a good example of how geologic, geodetic and seismologic studies can allow us to recognize the areas most likely to be the sites of strong earthquakes, even though it remains impossible to determine when exactly they will take place, at least not with a precision of hours or days. It has to be considered that geology operates on temporal scales of hundreds of thousands or millions of years, and thus even a "forecast" in a time window of 10 or 100 years would represent an excellent result. Almeno, non entro un intervallo temporale di ore o giorni. Knowledge of the areas with elevated probability of a strong earthquake is the first important step to reduce the impact of earthquakes. Also in the case of a poor country like Nepal, risk reduction policies can be adopted. We will discuss this in the next issue of the INGVnewsletter.
Giuseppe Mercalli Goes To The Expo
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Due appreciation by the research environment and the entire national italian community to a fundamental figure in the story of Italian seismology and volcanology: with this spirit, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) wishes to dedicate this introductory issue of the INGVnewsletter to the great Italian scientist Giuseppe Mercalli, known worldwide for having his name linked to the “scale” measuring the intensity of earthquakes. For a full year, a series of ventures has been designed to commemorate this seismologist, volcanologist, and teacher. Starting 19 March of last year, on the centenaryh of his death, this itinerary closes on the forthcoming 20 May at Milan, date and site of Mercalli’s birth, during the Expo 2015 events. “Feeding the planet – Energy for life” is the theme of Expo 2015, which from Milan expands all over our peninsula, which is made of excellence, centuries-long traditions, and culture. From volcanoes comes the concept of energy, which, converted into millennia of activity of these majestic manifestations of nature, is translated into fertility, uniqueness impossible to be imitated elsewhere in the world. If then the uniqueness of areas geologically so particular intersects with a historical and cultural parcourse across millennia, it is understandable how energy, geology, volcanism and development are the framework of the areas in our country which surround the 10 active volcanoes of Italy. A culture made of energy, the same energy that volcanoes have transmitted to the organoleptic characteristics of the areas around them, making them unique laboratories also for agricultural production, and thus not only for the scientists who study their ever so tiny variation. This initiative, which include salso a teaching course for journalists, is part of the scientific communication and information campaign fostered by the INGV on the occasion of the centenary. The Mercallian Year (annomercalliano.ingv.it) has received the High Patronage from the President of the Republic, the patronage from the Premiership and from the Ministry of Instruction, Universities and Research, and the recognition as an event of national interest from the Premiership’s scientific committee for anniversaries of national interest. Editorial After a period of being “under construction”, the INGVnewsletter is back with an innovative editorial formula: from the reorganization of the News and the new high-visual-impact graphic layout, to the enhanced use of images and video. Likewise, the concept of the contents has been renewed, giving the value of the scientific news and editorial attention a central position, in order to offer a guided reading experience, thanks to new strategies of link building, and being more and more interconnected. To the value of clear and timely information are added all the potentials offered by technology: a user experience platform close to touch objects, and a new version for tablets and smartphones with easily readable fonts. Also the graphic release has changed. The characters on the page are more brilliant, leaving major space to photos for horizontal and vertial reading of the newsletter. The subdivision of text, photos and videos is abandoned, offering the reader innately multimedia contents and the page of an article enriched with hypertext links, in-depth analysis, image galleries and video. Hierarchical order of the news permits rapid access to the agenda of the day, to articles strongly integrated with high-impact photo galleries, and windows always open to pertinent news. To appraise the specials, a video section has been added via the YouTube channel, whereas the Facebook page will give major visibility to the institute’s initiatives. The new INGVnewsletter uses the same graphic and fonts as the site INGVcomunicazione, a vista identical to the information page of the institute. Sincere thanks to all those who have contributed to the realization of this new editorial product: the working group consisting of the editorial staff, webmaster, webgroup, laboratory of graphics and video production coordinated by the Office of Communication, institutional and international and event activity, and Press Office. Hoping that the number of subscribers to the INGVnewsletter will grow vigorously, I wish all of you an enjoyable read. President Stefano Gresta