SHOCK: Type of tremor.

[Blank]: Main shock.

P - Precursor: Weaker tremor preceding an earthquake (referred to as the "main" tremor), in the same place.

R - Aftershock: Weaker tremor following an earthquake (referred to as the "main" tremor), in the same place.

E - Individual tremor in a swarm: (series of tremors of equal importance).

Z - Group of tremors in a swarm: (series of tremors of equal importance).

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Date: 
SisFrance dating of old earthquakes is based on the chronology of the Gregorian calendar (in France, 1582 reform) and takes into account ways of beginning the year (Christmas, Annunciation and Eater) used in various provinces until the 15th century.
e.g.: The earthquake on 1st March 1489 (Julian calendar) is listed as 1st March 1490 (Gregorian calendar).

Similarly, SisFrance establishes the correspondence between Republican and Gregorian calendars.
e.g.: The earthquake on 6 Pluviôse (fifth month in the Republican calendar) year 7 (Republican calendar) is dated 25 January 1799 (Gregorian calendar).

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EPICENTRE: point located on the surface of the earth vertical to the focus.

It is close to the epicentre that the effects of the earthquakes are strongest. Location indexes (co-ordinates) for the epicentre (longitude and latitude in degrees minutes sexagesimal) :

Code A (a few km): exact location in an area of maximum intensity well defined by an isoseismal line,

Code B (around 10 km): fairly certain location in an area of maximum intensity which is relatively well defined by an isoseismal line,

Code C (between 10 and 20 km): imprecise location in an area of maximum intensity which is insufficiently demarcated by an isoseismal line,

Code D (from a few km to 50 km): strongly assumed location in an area of macro-seismic intensity which is not limited by an isoseismal line.

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FALSE EARTHQUAKE: 
Event reported by accounts as a real earthquake but for which, after verification of the sources, the nature is similar to another type of phenomenon (landslide, collapse, mining rock burst or falling meteorite); in other cases, this may be the observance of an error in dating by an author of little faith.

DUBIOUS EARTHQUAKE: 
Event for which the arguments are insufficient to show its tectonic origin: date and location have not been able to be matched up and verified by various accounts; in other cases, the context (hurricane, violent storm) favour uncertainty.

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TIME: 
In SisFrance, the time of an earthquake is expressed in several ways:

in Universal Time (U.T.) almost generally from 1960 to date, more exceptionally before,

in Local Time (L.T.) for the other times,

by correspondence on old expressions e.g.: "vespers time" = around 5-6 p.m..

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Estimated indexes of the intensity linked to the observation: 

Code A Certain intensity,

Code B Fairly certain intensity,

Code C Uncertain intensity.

When the index appears alone, not accompanied by an intensity value, it means that the earthquake was felt in the location: in a certain manner (A), fairly certain (B) or uncertain (C).

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EPICENTRAL INTENSITY: intensity at the epicentre of the earthquake.

It is assessed using a macro-seismic map where all the intensities determined in various places are reported, according to the observations available. The epicentral intensity provides the means for expressing the size of a past earthquake. The intensity is generally greatest at the epicentre and decreases as one moves away from the epicentre. The rate of decrease is greater when the focus of the earthquake is not very deep. Analysis of all the intensities observed on an earthquake provides the means for determining the magnitude which provides an estimate of the energy dissipated at the focus in the form of seismic waves. For current earthquakes, statistical correlations may be established between intensity and magnitude according to the depth of the focus. These correlations in return provide the means for estimating the likely magnitude of past earthquakes.

Degrees of epicentral intensity:

4 moderate tremor felt inside and outside houses, objects shake,

5 strong tremor sleeping persons are woken up, objects fall, sometimes slight cracks in plasterwork,

6 slight damage sometimes cracks in walls, many people are frightened,

7 pronounced damage large cracks in the walls of many houses, chimney stacks collapse,

8 heavy damage the most vulnerable houses are destroyed, nearly all suffer significant damage,

9 destruction of many buildings sometimes of good quality, monuments and columns collapse,

10 general destruction of buildings even the least vulnerable (non-aseismic),

11 catastrophe all buildings are destroyed (bridges, dams, underground pipework, etc.).

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MACRO-SEISMIC INTENSITY: 
The macro-seismic intensity is the quantification of an earthquake's power at a particular point on the earth's surface, from a statistical estimate of the effects caused at that place, on people, buildings and the environment.
In SisFrance, the absence of an intensity value for a location corresponds to the fact that the details on the effects of the earthquake are lacking for that place. The earthquake is then considered as having been felt: in a certain manner (code A), fairly certain (code B)or uncertain (code C).

The intensity is assessed on a macro-seismic scale.
In France and in most European countries, the intensity is expressed on the M.S.K. 1964 scale (from the name of the people who devised it: Medvedev, Sponheuer and Karnik), which has 12 degrees expressed in Roman numerals to highlight the discrete nature of the degrees on the scale. For practical reasons, Arab numerals are used here. For current earthquakes, the recommended scale is the 1998 EMS (European Macro-seismic Scale) which is an update of the MSK scale more suitable to current buildings (in particular aseismic buildings).
Brief description of the M.S.K. 1964 intensity scale degrees
(M.S.K.: Medvedev, Sponheuer, Karnik: names of the people who devised it)

0 declared tremor not felt (value specific to SisFrance, outside the MSK scale),
1 tremor not felt but registered by instruments (value not used),
2 tremor scarcely felt in particular by people at rest and on upper floors,
3 tremor felt weakly hanging objects swing,
4 tremor largely felt inside and outside houses objects shake,
5 strong tremor sleeping people wake, objects fall, sometimes slight cracks in plasterwork,
6 slight damage sometimes cracks in walls, many people are frightened,
7 pronounced damage wide cracks in the walls of many houses, chimney stacks collapse,
8 heavy damage the most vulnerable houses are destroyed and nearly all of them suffer significant damage,
9 destruction of many buildings sometimes of good quality, monuments and columns collapse,
10 generalised destruction of buildings even the least vulnerable (non-aseismic),
11 devastating all buildings are destroyed (bridges, dams, underground pipework, etc.),
12 landscape change enormous crevices in the ground, valleys blocked, rivers moved.

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Effect:  Natural phenomena associated with the tremor and observed in the area.

MT - Earth movements,

RZ - Tsunami,

EE - Hydrological effects,

PL - Light effects,

ES - Site effects.

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EPICENTRAL INTENSITY QUALITY: intensity at the earthquake's epicentre.

This is assessed using a macro-seismic map where all the intensities determined in different places are reported, according to the observations available. The epicentral intensity provides the means for expressing the size of a past earthquake. The intensity is generally greatest at the epicentre and decreases as one moves away from the epicentre. The rate of decrease is greater when the focus of the earthquake is not very deep. Analysis of all the intensities observed on an earthquake provides the means for determining the magnitude which provides an estimate of the energy dissipated at the focus in the form of seismic waves. For current earthquakes, statistical correlations may be established between intensity and magnitude according to the depth of the focus. These correlations in return provide the means for estimating the likely magnitude of past earthquakes.

Epicentral intensity assessment indexes:

Code A: Certain epicentral intensity, estimated according to a tight distribution and an exact value of maximum limited intensities,

Code B: Fairly certain epicentral intensity, estimated according to a less tight distribution and an exact value of maximum limited intensities,

Code C: Uncertain epicentral intensity, estimated according to a scattered distribution and an imprecise value of limited intensities.

Code K: Fairly certain epicentral intensity, resulting from a calculation based on an attenuation law (Sponheuer).

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DOCUMENTARY SOURCES: 

SisFrance is dependent on documentation detailing in writing the effects of past earthquakes. To justify the seismicity in metropolitan France and the areas around it, although SisFrance provides the descriptive bibliography of the events in accordance with a state of knowledge which is updated annually, this site also proposes, with agreement from the Direction des Archives de France (French Archives Division) a certain number of digitised documents which are accessible for display and subject to reproduction rights.

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INFORMATION ON TRANSCRIPTION: 

The transcription of documents offered by SisFrance is intended to meet a double objective

to make intelligible the content of documents for which the calligraphy does not lend itself to easy reading,

to distribute the content of documentary sources for which it has not been possible to reproduce the original.

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