Impact Feature: Bussana Vecchia
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Location Old Bussana is a 1,000 year old ghost town in Liguria, a few kilometers from the Italian-French border. It is administratively part of the city of Sanremo. The City was built in the first half of the 9th century on top of a hill. Here you can see the full impact of a disastrous Earthquake. The Region of Liguria The French Riviera and western Liguria are at the junction of south-western Alps and Liguria basin, a region of normally moderate seismicity. Liguria is a narrow strip of land. It is one of the smallest regions in Italy. Its shape is that of a thin strip of land, from 7 to 35 km comprised between the sea and the watershed line of the Maritime Alps and the northern Apennines. Some mountains rise above 2,000 .The continental shelf, which is very narrow, is so steep it goes down almost immediately to considerable marine depths. The Earthquake Eartquakes (tremors) are sudden releases of energy in the Earth´s crust. They create seismic waves. The severest earthquake to hit Bussana struck the region on February 23, 1887 killing more than 2000 people. The worst of the damage in Bussana occurred at 6:21 on that Ash Wednesday morning, a twenty second seismic wave caused immediate destruction and deaths throughout the village. Tectonic plates or why does the Earth shake Not visible for us directly the Earth is divided into 8 big tectonic plates and 6 minor plates. These plates ride on the liquid parts of the mantle. The plates move in relation to one another at one of three types of plate boundaries: convergent, or collisional boundaries; divergent boundaries and transform boundaries. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The lateral movement of the plates 5 -10 centimeters annually. Tectonic plates are able to move because the Earth's lithosphere has a higher strength and lower density than the underlying asthenosphere. Their movement is driven by heat dissipation from the mantle. These movements are follwed by strong eruptions building up pressure that spontaneously erupts and leads to earthquakes. Here at the Liguria – Region the junction of south-western Alps and Liguria is responsible for tremors. The narrow but high continental shelf connected with considerable deep water side at the Bussana area may have worked as an amplifier to a small tremor leading to severe damages in 1887. Measurement of tremors There are three popular methods to measure the strength of an earthquake: a) The Richter magnitude scale b) The moment magnitude scale c) The Mercalli-Cancani-Sieberg scale a) The Richter magnitude scale assigns a number to quantify the amount of seismic energy released by an earthquake. It is a base-10 logarithmic scale and measures the largest displacement from zero on seismometer output. An earthquake that measures 4.0 on the Richter scale has a shaking amplitude 10 times larger than one that measures 3.0. The Richter scale is still widely used in the media and very popular. It is named after Charles Richter who - in partnership with Beno Gutenberg – developed the system in 1935. b) Today´s seismologists use the moment magnitude scale to measure the size of earthquakes in terms of the energy released. The magnitude is based on the moment of the earthquake, which is equal to the rigidity of the Earth multiplied by the average amount of slip on the fault and the size of the area that slipped. It was introduced in 1979 by Caltech seismologists Thomas C. Hanks and Hiroo Kanamori. c) The Mercalli scale was developped by Italian scientistt Giuseppe Mercalli between 1884 and 1906. It was later completely re-written by the German geophysicist August Heinrich Sieberg re-named into Mercalli-Cancani-Sieberg (MCS) scale. The twelfepart table give us an easy measure to classify to strength of an earthquake by the way individuals feel the shake and the structural damage it causes. Typical classification of Earthquakes (MCS-scale) Strength Classification and Interaction with mankind and environment 1 Instrumental Not felt by many people unless in favourable conditions. 2 Feeble Felt only by a few people at best, especially on the upper floors of buildings. Delicately suspended objects may swing. 3 Slight Felt quite noticeably by people indoors, especially on the upper floors of buildings. Many do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration similar to the passing of a truck. Duration estimated. 4 Moderate Felt indoors by many people, outdoors by few people during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rock noticeably. Dishes and windows rattle alarmingly. 5 Rather Strong Felt outside by most, may not be felt by some outside in non-favourable conditions. Dishes and windows may break and large bells will ring. Vibrations like large train passing close to the house 6 Strong Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken; books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight. 7 Very Strong Difficult to stand; furniture broken; damage negligible in building of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by people driving motor cars. 8 Destructive Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture moved. 9 Ruinous General panic; damage considerable in specially designed structures, well designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. 10 Disastrous Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundation. Rails bent. 11 Very Disastrous Few, if any masonry structures remain standing Bridges destroyed. Rails bent greatly. 12 Catastrophic Total damage - Everything is destroyed. Total destruction. Lines of sight and level distorted. Objects thrown into the air. The ground moves in waves or ripples. Large amounts of rock move position. To log this Cache please e-mail the answers to the following question to me and log directly online. I will come back to you in case of incorrect answers: 1) How would you rate the strength of the earthquake happening 1887 using the MCS scale? 2) Describe in your own words what happened to the church`s altar and the roof? If you like to please attach a photo to your log (this is a volunteer rule). Tscherman: Bussana Vecchia ist eine ca. 1100 Jahre alte Stadt in Ligurien. Im Februar 1887 gab es hier ein verheerendes Erdbeben und mehr als 2000 Menschen starben in dessen Folge. Die Ligurische Küste liegt steil abfallend an einer der Tektonischen Platten der Erde. Die Anhöhe auf der Bussana liegt kann als Verstärker für Erdbeben dienen. Die Stärke von Erdbeben kann durch verschiedene Verfahren bestimmt werden: 1) die Richter-Skala 2) die Moment-Auslenkungs-Skala 3) die Mercalli Skala Am bekanntesten ist sicherlich die Richter Skala, die sie in den Medien am häufigsten verwendet wird. Ich möchte an dieser Stelle, aber besonders auf die Mercalli Scala eingehen. Die Mercalli Skala klassifiziert die Stärke eines Erdbebens anhand dessen Auswirkungen (Impact) und macht Erdbebenstärken "anschaulich". Die 12 geteilte Skala ist wie folgt aufgeteilt: 1) Instrumental Messbares Erdbeben 2) Erahnbares Erdbeben, das vo empfindlichen Personen wahrgenommen wird 3) Leichtes Erdbeben, dass sich wie die Vibrationen eines LKWs im Vorbeifahren anfühlt 4) Moderates Erdbeben: Geschirr in Schränken wackelt deutlich 5) Ziemliches starkes Erdbeben: Fühlt sich an, als würde ein Güterzug direkt am Haus vorbeifahren. 6) Starkes Erdbeben: Bücher fallen um, Geschirr zerbricht 7) Sehr starkes Erdbene: schwierig zu stehen 8) Zerstörerisches Erdbeben: Zerstörung von Dächern und Wänden 9) Ruinöses Erdbeben: Zersörung von größeren Gebäuden 10) Desaströses Erdbeben: Zerstörung von Häusern unklusive Grundmauern 11) Sehr Desaströs: Zerstörung von Brücken und Tunneln 12) Katastrophales Erdbeben: Totale Zerstörung, Aufbrechen des Bodens, Verschiebung von Bergen Um diesen Cache zu loggen beantwortet bitte die Fragen per e-Mail und wenn möglich, stellt ein Bild in die Galerie zu euren Log. Fragen: 1) Wie würdet ihr das Erdbeben auf der Mercalli Scala einstufen? 2) Was passierte mit dem Altar und dem Dach der Kirche? Ihr könnt direkt loggen. Sollte etwas nicht stimmen oder kein Mail angekommen sein, melde ich mich. Viel Spaß in Ligurien und in Bussana Italian: Bussana Vecchia Bussana Vecchia è una frazione collinare del Comune di Sanremo. Il violento terremoto del 23 febbraio 1887 semidistrusse il paese, fino a quel momento chiamato semplicemente "Bussana", tanto da venire completamente evacuata dagli abitanti che si spostarono circa tre chilometri più a valle fondando il paese di Bussana Nuova. Totalmente abbandonata per decenni, ha ricominciato ad essere abitata dal finire degli anni cinquanta del Novecento da artisti italiani e stranieri, attratti dalla particolarità del luogo, che ristrutturarono e resero nuovamente abitabili gli edifici meno danneggiati. Attualmente ospita una comunità internazionale di artisti, con botteghe artigiane ed alcuni punti di ristoro, tanto da essere divenuto, negli anni, un caratteristico "villaggio di artisti" in un'ambientazione da borgo medioevale. Terremoti: I terremoti, detti anche sismi o scosse telluriche, sono vibrazioni improvvise, rapide e più o meno potenti della crosta terrestre, provocate dallo spostamento improvviso di una massa rocciosa nel sottosuolo. Misura: La scala Mercalli è una scala che misura l'intensità di un terremoto tramite gli effetti che esso produce su persone, cose e manufatti. Sistema: Grado, Scossa, Descrizione: 1. strumentale: avvertita solo dagli strumenti per la rilevazione dei terremoti 2. debole: avvertito solo da poche persone sensibili in condizioni particolari 3. leggera: avvertito da poche persone 4. moderata: avvertito da molte persone; tremiti di infissi e cristalli 5. piuttosto forte: avvertito da molte persone, caduta di oggetti 6. forte: qualche lesione agli edifici 7. molto forte: caduta di comignoli; lesione agli edifici 8. distruttiva: rovina parziale di alcuni edifici; vittime isolate 9. rovinosa rovina: totale di alcuni edifici; molte vittime umane; crepacci nel suolo 10. disastrosa: crollo di parecchi edifici; innumerevoli vittime umane 11. catastrofica: distruzione di agglomerati urbani; moltissime vittime 12. danneggiamento totale: distruzione di ogni manufatto; pochi superstiti 13. devastazione totale: completa distruzione della zona interessata; possibile sprofondamento del territorio A sccrivere su, si preaga risondere alle domande: 1) Quanto forte e stato il terreonta in base alla scale (sistema Mercalli)? 2) Coas e sucesso al tetto della chiesa? Invia una e-mail con la rispota me. Puoi inscriverti adesso. Se qualcosa non va, mi alzo. Saluti, absentax
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