I grado

Impercettibile: rilevato soltanto da sismografi.

II grado

Molto leggero: sentito soltanto da persone estremamente sensibili o nervose, in perfetta quiete e quasi sempre nei piani superiori dei caseggiati.

III grado

Leggero: anche in zone densamente abitate viene percepito come terremoto, soltanto da una piccola parte degli abitanti nell'interno delle case, come nel caso del passaggio di un pesante mezzo. Da alcuni viene riconosciuto come terremoto soltanto dopo averne parlato con altri.

IV grado

Moderato: all'aperto il terremoto e` percepito da pochi. Nelle case e` notato da numerose persone ma non da tutti, a seguito del tremolio o di oscillazioni leggere di mobili. Cristalleria e vasellame, posti a breve distanza, urtano come al passaggio di un pesante autocarro su strada dissestata. Finestre tintinnano; porte, travi e assi in legno scricchiolano; cricchiano i soffitti. In recipienti aperti, i liquidi vengono leggermente mossi. Si ha la sensazione che in casa si sia rovesciato un oggetto pesante; si oscilla con tutta la sedia o il letto come su una barca. In generale questi movimenti non provocano paura a meno che le persone non si siano innervosite o spaventate a causa di terremoti precedenti. In rari casi i dormienti si svegliano.

V grado

Abbastanza forte: nel pieno delle attivita` giornaliere, il sisma viene percepito da numerose persone nelle strade e se sensibili anche in campo aperto. In casa si avverte in seguito allo scuotere dell'interoedificio. Piante e piccoli rami di cespugli ed alberi si muovono con evidenza, come se ci fosse un vento moderato. Oggetti pendenti come lampade, tendaggi, lampadari non troppo pesanti entrano in oscillazione, campanelle suonano. Gli orologi a pendolo si fermano od oscillano con maggior periodo, a seconda della direzione della scossa se perpendicolare o normale al moto di oscillazione. A volte orologi a pendolo fermi riprendono il movimento. La luce elettrica guizza o viene a mancare in seguito a movimenti della linea. I quadri urtano, battono contro le pareti oppure si spostano; da recipienti colmi e aperti vengono versate piccole quantita` di liquido; ninnoli ed oggetti del genere possono cadere come pure gli oggetti addossati alle pareti; arredi leggeri possono essere spostati di poco; mobili rintronano; porte ed imposte sbattono; vetri delle finestre si infrangono. Quasi tutti i dormienti si svegliano. Sporadici gruppi di persone fuggono all'aperto.

VI grado

Forte: il terremoto viene notato da tutti con paura, molti fuggono all'aperto, alcuni hanno la sensazione d'instabilita`. Liquidi si muovono fortemente; quadri, libri e cose simili cadono dalle pareti e dagli scaffali; porcellane si frantumano; suppellettili assai stabili, e perfino pezzi d'arredo vengono spostati se non rovesciati; piccole campane in cappelle e chiese, e orologi di campanili battono. Case isolate, solidamente costruite subiscono danni leggeri; spaccature all'intonaco, caduta del rinzaffo di soffitti e di pareti. Danni piu` forti, ma non ancora pericolosi, si hanno sugli edifici mal costruiti. Qualche tegola e pietra di camino cade.

VII grado

Molto forte: notevoli danni vengono provocati ad oggetti di arredamento anche di grande peso. Grandi campane rintoccano. Corsi d'acqua, stagni e laghi si agitano e s'intorbidiscono a causa della melma mossa. Qua e la`, parte delle sponde di sabbia e ghiaia scivolano via. Varia la portata delle sorgenti. Danni moderati a numerosi edifici costruiti solidamente: piccole spaccature nei muri; caduta di toppe piuttosto grandi dell'incalcinatura e dello stucco, a volte anche di mattoni. Caduta generale di tegole. Molti fumaioli vengono lesi da incrinature. Camini gia` danneggiati si rovesciano sopra il tetto danneggiandolo. Da torri e costruzioni alte cadono decorazioni mal fissate. Quando la casa e` a pareti intelaiate, i danni all'incalcinatura e all'intelaiatura sono piu` gravi. In casi isolati distruzione di case mal costruite oppure riattate.

VIII grado

Rovinoso: interi rami d'albero pendono rotti e perfino si staccano.Anche i mobili piu` pesanti vengono spostati lontano e a volte rovesciati. Statue, monumenti in chiese, in cimiteri e parchi pubblici, ruotano sul proprio piedistallo oppure si rovesciano. Solidi muri di cinta in pietra si rompono e crollano. Circa un quarto delle case e` gravemente leso, alcune crollano, molte diventano inabitabili; gran parte di queste cadono. Negli edifici intelaiati cade gran parte della tamponatura. Case in legno vengono schiacciate o rovesciate. Spesso campanili di chiese e di fabbriche con la loro caduta causano danni agli edifici vicini piu` di quanto non avrebbe fatto da solo il terremoto. In pendii e terreni acquitrinosi si formano crepe. In terreni bagnati si ha l'espulsione di sabbia e di melma.

IX grado

Distruttivo: circa la meta` di case in pietra sono distrutte; molte crollano; la maggior parte diviene inabitabile. Case ad intelaiature sono divelte dalle proprie fondamenta e crollano; travi strappate a seconda delle circostanze contribuiscono alla rovina.

X grado

Completamente distruttivo: gravissima distruzione di circa 3/4 degli edifici, la maggior parte crolla. Perfino costruzioni solide di legno e ponti subiscono gravi lesioni, alcuni vengono distrutti. Argini e dighe ecc., chi piu`, chi meno, sono danneggiati notevolmente, binari leggermente piegati e tubature (gas, acqua e scarichi) vengono troncate, rotte e schiacciate. Nelle strade lastricate e asfaltate si formano crepe e per pressione sporgono larghe pieghe ondose. In terreni meno densi e piu` umidi si creano spaccature fino alla larghezza di piu` decimetri; si notano parallelamente ai corsi d'acqua spaccature che raggiungono larghezze fino a un metro. Non solo pezzi di terreno scivolano dai pendii, ma interi macigni rotolano a valle. Grossi massi si staccano dagli argini dei fiumi e da coste scoscese; riviere basse subiscono spostamenti di masse sabbiose e fangose, per cui il livello del terreno viene notevolmente variato. Le sorgenti subiscono frequenti cambiamenti di livello dell'acqua. Da fiumi, canali e laghi ecc. le acque vengono gettate contro le sponde.

XI grado

Catastrofico: crollo di tutti gli edifici in muratura, resistono soltanto le capanne di legno e le costruzioni ad incastro di grande elasticita`. Anche i ponti piu` sicuri crollano a causa della caduta di pilastri in pietra o del cedimento di quelli in ferro. Binari si piegano fortemente e si spezzano. Tubature interrate vengono spaccate e rese irreparabili. Nel terreno si manifestano vari mutamenti di notevole estensione, a seconda della natura del suolo, si aprono grandi crepe e spaccature; sopratutto in terreni morbidi e acquitrinosi il dissesto e` considerevole sia orizzontalmente che verticalmente. Ne segue il trabocco di sabbia e melma con diverse manifestazioni. Sono frequenti lo sfaldamento di terreni e la caduta di massi.

XII grado

Grandemente catastrofico: non regge alcuna opera dell'uomo. Lo sconvolgimento del paesaggio assume aspetti grandiosi. Corsi d'acqua sia superficiali che sotterranei subiscono mutamenti vari, si formano cascate, scompaiono laghi, fiumi deviano.

MCS Scale of seismic intensity C. Davison (1921), Bull. Seism. Soc. Am., 11, 95-129.

 

 

1°. Imperceptible. The shock is not felt by man; only the records of seismometers adapted for earthquakes of near origin, or of sensitive seismoscopes give notice of it.

2°. Very slight. Only a few persons in perfect repose, especially those with sensitive nerves, feel the shock as a slight tremor or rocking. The shock is especially sensible on the upper floors of houses and very rarely on the ground floor. Also, the quiet of the night is favorable to its perception, if the observer is awake.

3°Slight. Even in densely populated districts, the shock is felt by only a few persons as a shaking like that produced by the rapid passing ­of a wagon. Occasionally, the duration, and perhaps also the direction, of the movement can be detected. Many only realize afterwards, in talking with others, that there has been an earthquake.

4°. Moderate. Of persons in the open air, not many feel the earth­quake. Indoors, many persons, but not all, recognize the trembling or slight rocking movement of furniture; glasses and crockery near to­gether gently strike one another as they do when a heavily laden wagon is driven by on an uneven pavement; windows rattle; doors, joists, floors, and ceilings creak; liquids in open vessels are slightly moved. Alarm is hardly ever caused except in the case of persons who have already become nervous and anxious through the experience of other earthquakes. In a few cases, sleepers awake.

5°. Rather strong. Even during the busiest hours of the day, the earthquake is felt by many persons in the open air. Indoors, the shak­ing of the whole building is generally noticed, the feeling being the same as when some heavy object (such as a sack or piece of furniture) falls in the house; or the observers move, together with chair, bed, etc., as in a ship on an agitated sea. Plants, the branches and weaker boughs of shrubs and trees sway visibly, as they do with a moderate wind. Freely hanging objects, such as curtains and lamps, but not heavy chandeliers, oscillate; small bells ring; the pendulums of clocks are stopped or swing more widely according as the direction of the shock is at right angles or parallel to the plane of oscillation; similarly, stopped pendulum clocks are set going; the striking spring of clocks sounds; electric lights fail to act when contact of the conducting wire is made; pictures rattle against the walls or are displaced; small quantities of liquid are spilt out of well‑filled open vessels; ornaments, small stand­ing frames fall and also objects leaning against the wall; even light furniture may be somewhat shifted from its place, rattling of furniture; doors and window‑shutters open or shut; window‑panes crack. Sleep­ers as a rule are awakened. A few persons run into the open air.

6°. Strong. The earthquake is felt by everyone with alarm, so that very many persons run into the open air, many thinking that they must fall. Liquids move violently, pictures fall from the walls, books, etc., from shelves, unless the direction of the shock is parallel to that of the walls; numerous vessels are broken; a few pieces of stable furniture are shifted or overturned; church bells and church clocks strike. In a few solidly built mid‑European houses there are cracks in the plaster, which is detached here and there in fragments from the roof and walls. In poorly built houses, the damage is greater, but still not of a serious nature.

7°. Very strong. Considerable damage is done to furniture through the upsetting or breaking even of heavy pieces. Even large church bells strike. The surfaces of rivers, ponds, and lakes are disturbed, and the mud at the bottom stirred up. A few slips of sandy and gravelly coasts. The level of water in wells is changed. Notwithstanding their solid construction, many mid‑European houses suffer moderate dam­age; there are slight fractures in walls, large pieces of plaster crumble down, tiles fall, pantiles are loosened and slip down. Chimneys are damaged by cracks and by the falling of weather moulding and stones; chimneys in bad condition break off at the roof and injure it. Badly fastened decorations fall down from towers and high buildings. In framework buildings, and especially in their partition walls, the dam­age to the plastering is great. Buildings that are badly built or out of repair suffer seriously in the same way; wooden fences, sheds, high enclosure walls, cottages and even churches, minarets of mosques, etc., in many country districts of southern Europe, fall down to a greater or less extent. Earthquake‑proof buildings, such as most of the stone and wooden houses in Japan, and the wood and wattled buildings, which are used in such great quantities in tropical earthquake‑districts, remain quite undamaged.

8°. Ruinous. The trunks of trees, of palms especially, sway as with a strong wind. Even the heaviest pieces of furniture are shifted some distance or overturned. Statues, etc., near the ground, such as those in churches, churchyards, public parks, etc., either rotate on their pedestals or fall. Stone enclosure‑walls are split and thrown to the ground. Notwithstanding their solid construction, mid‑European houses suffer serious damage, with gaping cracks in the masonry; in some cases, they collapse partly; most chimneys fall; church towers and factory chimneys especially so suffer, and, by their fall, neighboring houses may be more seriously damaged as if by the action of the shock alone; exceptionally well‑built factory chimneys are only fractured and displaced in their upper portions. Earthquake‑proof buildings (such as those of Japan) show, slight damage, such as fractures, the crumbling of plaster, etc. (see degree 7, mid‑European houses), and wooden houses crack considerably in their joints. Rotten posts of Malayan stake‑huts break. Slight cracks in the ground near steep slopes and in damp soil; a few outflows of water carrying small quantities of sand or mud.

9°. Disastrous. Solidly built houses of European construction are seriously damaged, so that a large number becomes uninhabitable, a few fall completely or nearly so. Framework buildings are displaced on their stone foundations, on account of which they are under certain conditions damaged. Earthquake‑proof buildings made of stone show considerable damage, the walls of wooden ones reveal gaps and cracks, old wooden houses are loosened in their frames.

10°. Destructive. Most stone and framework buildings are over­thrown together with their foundations, even first‑class brick walls show dangerous cracks, but the percentage of those of mid‑European construction is larger than in the case of earthquake‑proof buildings. Even well‑built wooden houses and bridges suffer serious damage, a few are even demolished. Embankments, dams, etc., are more or less considerably damaged. Iron railway‑lines are slightly bent. Conduit pipes (gas, water, etc.) in the ground are rent or compressed. Fis­sures and undulating folds are formed in the asphalt of the streets. Loose, and especially damp, ground shows fissures up to several deci­meters in width; especially near water‑courses, there may be parallel fissures from one‑half to three‑quarters of a meter wide. Not only does loose ground slide down from cliffs as landslips, but also rock­slides fall into the valleys from the mountains, from the banks of rivers and even steep coasts whole parts break off, and on flat coasts masses of sand and mud are displaced, by which substantial changes in the form of the ground are wrought. The level of water springs is changed. From rivers, canals and lakes, water is thrown on to the banks.

11°. Catastrophe. Stone buildings of whatever kind practically no longer stand. Even solid buildings of wood or wattling are only in a few cases able to survive, especially near lines of faulting. Bridge-­buildings, though large and securely constructed, are destroyed by the breaking off of massive stone piers or fracture of iron shafts. Yielding wooden floors, however, are sometimes less damaged. Embankments and dams are quite torn asunder, frequently for long distances. Iron rails are strongly bent and compressed. The kind and amount of damage to roads depends on the nature of the foundations. Conduit pipes in the ground are completely severed and rendered useless. The most varied and very considerable morphological changes of the ground are noticed, which are closely defined by the nature of the ground; wide fissures and cracks are formed, the derangements in the horizontal and vertical directions being specially important in soft and watery ground. There is also the appearance in various forms of water carrying sand and mud. Landslips and rocks‑falls are numerous.

12°. Great catastrophe. No work of human hands remains stand­ing. The derangements and transformations of the ground attain the grandest dimensions. Even in rocky ground, faults of considerable depth are formed, with great horizontal movements and numerous fissures. Dock cliffs break, rock‑falls, landslips, collapse of river banks or shore are numerous and widespread. Underground and sur­face waters in consequence undergo the most various derangements; waterfalls are formed, lakes are dammed, rivers diverted, etc.