MARTINEZ-GUEVARA, J.B.; SAURA RAMOS, S. (1988)

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ESC, Sofia-Bulgaria 1988. Symposium S5: Calibration of Historical Earthquakes in Europe and recent developments in intensity interpretation

Index

Abstract
Introduction
Structure of the  Database
Conclussion
Figures
Bibliography
Map

ABSTRACT.-

This paper exposes the results obtained from the research about historical seismicity which took place in the "Comunidad Autónoma de la Región de Murcia" (Spain). For this research a database was created in which, annually, the available historical information is revised, all the documentation is evaluated, and more information in historical archives is pursued and recorded. The criteria followed to define the database and its scheme are also presented. The records include factors of quality (FQ) of the parameters which define the earthquake.
From this primary database and by a selective method, reports connecting all the elements of each record or just part of them can be created, as well as secondary databases in which partial information of the primary would be trasferred.

Index

A general study in Historical Seismicity is being made by the government of the Autonomous Community of Murcia (Spain), as a part of an agreement between both the Autonomous Community and the National Geographic Institute of Spain (I.G.N.). It is a part of the "Project of Evaluation related to Historical Seismicity in the Mediterranean Countries", by I.A.E.A..
The authors of this presentation, who are members of a group of research in that general study, have enlarged what was mainly a compilation of sources related to seismic information with intensities higher or similar to V in the M.S.K. scale. It helps the database to keep all the information concerning the study of historical seismicity, as well as other further studies of enlargement and maintenance of the databases which have been created for that purpose. It has been foreseen the use of this information both historical and instrumental means of defining appropriate fields for both categories of data including, as usual, factors of quality for those concepts which could be interpreted in different ways or subject of later revision. It has also been taken in account the fact that the general study to which we are referring, as well as other studies which are being made in Spain, will be culminated with a data base of historical seismicity in the IGN and its base will be the existing one. That is the reason why in our database fields codes of reference already used by IGN and others with a similar structure are used. On the other hand, the implantation of a database of this kind aims to the same purposes of the project INT/9/006 of the I.A.E.A. in the "Project Description seismic data for nuclear power plant siting" ^{(1) See GÜRPINAC, 1(1987,5)}
Let us define the organisation of the database, field by field, the information to be introduced in every one of them, as well as the versatility of the base in order to use some of the data in it and/or secondary bases of more specific information and to connect with other bases, etc.

Index

The mechanism of the database consists on creating card indexes for every earthquake. This will let us know on the one hand the date with which they are defined by the authors who study them, and on the other, the different sources which they have used.
The fields of the database, their type (character, numerical or date), broadness (maximum number of characters that can be used, including punctuation marks and decimal if necessary) and their description are the following:

STRUCTURE OF A DATABASE OF HISTORICAL EARTHQUAKE INFORMATION

This is a field with four characters which expreses the year of the Christian Era in which the earthquake took place.
It is defined as alpha mumeric to combine letters, signs and numbers, in such a way that it will be possible to represent, for example the year "12¿?" when referring to an unknown year of the XIIIth century (AD).
The Spanish Era, The Jewish Calendar, The Hegira, The Julian Calendar, the variations of The Incarnation and Nativity of Jesus, The Gregorian Reform of The Council of Trento are, among others, different computations which have been used in the Iberian Peninsula since the first century B.C., with jumps of dates, readjustments, overlaps and exceptions which oblige us to use tables of conversion.

The month of the year is expressed with two digits which are defined as alpha-numerical because of the same reason as in the 01 field. In this case "00" means an unknown month and "¿?" a doubtful month. The different months are expressed with the ordinal which they have in the Gregorian calendar, with "0" before the first nine months.

As well as the two preceding fields, which together with this express the whole date in which the earthquake took place, it is defined as a character type field with two numbers.
The whole date which identifies an earthquake is expressed in the following way: YYYY/MM/DD (year, month, day)

It is a field of one character, in which it can be stated from "A" to "D" (fig. 1) a decreasing degree of fiability of the whole date, and it is possible to use "=" or "¿?" as in preceding fields to indicate that the date is whether unknown or doubtful. Moreover, this inaccuracy can be qualified with one of the four degrees of the factor, what brings a greater accuracy in the quality of the date.

Time is defined in hours (from 01 to 24) minutes and tenths of a minute^{(2) see RODRIGUEZ DE LA TORRE, F. (1987)} . An "H" is written between hours and minutes and a "." between minutes and tenths. The origin time "00H00.0" means unknown time. "24H00.0" is used for the midnight.

Here we use the same symbols and degrees as in the 04 field (fig.1)

07 nature of event.-

Here we define if we are dealing with an earthquake, a false earthquake or a doubtful one, using the symbols "S", "F" and "D" respectively (fig. 2) .
We have already pointed out, in other studies, that it is convenient to state the information of earthquakes which later on were proved to be false or wrong. The qualification "false" could be proved later on as wrong; and even if it wouldn't be so, the inclusion as a "false" or doubtful earthquake is useful as a starting point for further investigations.

This field remains empty when the information is referred to the main earthquake; on the contrary, different symbols are used (fig. 3) to represent an aftershock, a premonitory, a swarm, an epicentre at sea (with the characters related to the place outside the sea where it is felt with greater intensity), a volcanic eruption, the beginning of a series of earthquakes, the last aftershock which is felt, or the existence of an isoseismal maps.

It is specified here the geographic longitude of the epicentre in degrees, minutes and tenths of a minute. Since all the longitudes of the area of our study are west of the Meridian of Greenwich, we do not specify it.

It refers to the geographic Latitude of the epicentre which is expressed in degrees, minutes and tenths of minute. Because of similar reasons as in the preceding field, it is not expressed that all the epicentres are north latitude.
The shape (form) of both coordinates will be "99°99.9" ("9" means any number).

The symbols and degrees which define the factor of quality of the coordinates are represented in fig. 4.^{(3) trasnlated by Angnès LEVERT (1987,156)}

Despite of the fact that we express the intensity according to the M.S.K.scale, which uses roman numbers to express the degrees, we define this field as numerical; we can use ".5" to express that the intensity varies between one degree and the next; i.e. : the intensity VIII-IX will be recorded as "8.5".

The factor of quality of the highest intensity (I0) is defined in fig. 5.(See footnote no. 3)

As we have pointed out in the introduction, this parameter, together with the five which follow^{(4) see MEZCUA, J. et al. (1983, 9),} are used to inform about earthquakes from the instrumental time. This admits a number and a decimal.

We call depth to the hipocentre expressed in Kilometres, with two numbers.

These patterns are used to define earthquakes from the instrumental time.

If the epicentre is situated in a town, its name should be mentioned; if not, the nearest one.
It can be used the two first characters of ten, which constitute the field, as "¿?" to indicate that the name is doubtful regardless the factor of quality of the coordinates.
It has been pointed out that is preferable to transcribe literally the name as it is expressed in the source with its development or known name as well as to point out the posible mistake with similar names. An example could be the following: an earthquake in Aguilas (Murcia-Spain) in november, 6th of 1762, was considered doubtful by the authors who studied it. Sánchez Navarro-Neumann transcribed the note by J. Milne: "Aquila (Spain)", and later on it was discovered that he was mistaked, because when copying from the French A. Perrey the date about earthquakes from Italy and Spain in two publications with similar names (one is "Sur les tremblements de terre de la Péninsule Ibérique" and the other "Memoire sur les tremblements de terre de la Péninsule Italique"), he made an error, situating Aquila in Spain. From this, some Spanish authors interprete Aquila as Aguilas (Spain).^{(5) see MARTÍNEZ-GUEVARA, J.B.; FERNÁNDEZ NAVARRO-SOTO, S. (1987a,50)}

The first five numbers are the official and administrative division in provinces and townships in Spain. It has been used traditionally a subdivision of the townships which have been called "entities" (singular or collective) of population. For these we use the same criteria and codes that the I.N.E. "Instituto Nacional de Estadística" (National Institute of Statistics) use for the census of population in Spain (Nomenclator). The whole code includes:
Province (2 numbers)
Township (3 numbers)
Collective entity (2 numbers)
Singular entity (2 numbers)

These patterns are similar to the fields 9, 10, 11, 12 and 13, respectively.
By second location we mean every place we know in which an earthquake ocurred, considering the epicentre as the first location. There will be a card-index for every second location.

These are similar to the fields 20 and 21 .

We point out the natural effects associated to the earthquake. If the effects were induced, the first character of this field would be "E" and if not it would remain empty, although some of the symbols represented on the the fig. 6 would be written.
The natural effects are always referred to the second location. So when you want to point any of them referred to the epicentre, the data of the second location will be empty.

This is a field of 8 characters in which the social effects produced by earthquake are codified, and taking into accont the following aspects:

• VICTIMS

• INJURED

• PSICOLOGICAL

• ABANDONMENT

• DAMAGES

We used five degrees for the first and fourth aspects, three degrees for the second and four for the third. Equal degree number does not mean that there is an equivalence among the four aspects. However, some of them match with the intensities of M.S.K. scale (fig.7).
The value of every one of the social effects is written at the bottom on the right hand corner of every square, and the final value is the alpha-numeric adition of the different parts; the order of the columns of the fig.7 is followed. When one or more aspects have not been studied "00" should be written. I.e.: the code "V2H1P4A5 " means that the earthquake has produced some victims (V2), light wounded people (H1), that people got into panic (P4) and general abandonment (A5)

The bibliography has a number of reference to be identified properly. We use the same number of identification like I.G.N. (Instituto Geográfico Nacional). The works which are not catalogued by I.G.N. will have a negative number in the identification, while they are not catalogued. Those number will coincide with the one in other specific database (in which the description and bibliographic location are pointed out with more detail) to which we can relate.

For every author we define a code of five characters which usually coincides with the initial of their name. In the case of two authors we join their initials with the latin conjunction "&" (i.e. "M&MS" means J. Mézcua and J.M. Martínez Solares); when there are more than two authors we follow the same process as in cataloging, that is, putting the first of them followed by "&al" (et alii) (i.e. "V&al" refers to L.A.M. Victor et al.).

The year of publication of the bibliographic reference.

Here we indicate the first page of the publication where the information about the earthquake is.

We refer to the classification of the bliography and sources, together with a criticism of the bibliography (figs. 8 and 9). This field, which has four characters, use the first two to clasify and others for criticism. I.e.: a book which has been classified as "specific bibliography with first hand sources" (B3), of "geological character and some conclussion" (E2), will have the code "B3E2".

We follow the same criteria used in fields 31 to 35.

We prefere to include the whole text from the sources, though by methodological reasons we record the texts individually separated from the database, with a code to indentify them. So here appears the date of the earthquake (year, month and day) and the number of reference of the source (field 36) separated by a stop.

There are 134 characters for observations which may be out of the defined fields.

Finally, we include here the date (day, month and year) of updating of every card-index that is concerned.

Index

The adecuate use of this database leads us to a better way for taking decisions about urban planning. This also allows us to make a rational reduction of the seismical risk. The information of the database is affected by quality factors which, carefully applied, can make more accurate its analysis. The easiness of being able to modify and/or appending fields to the database makes it operative and versatile, in relation with the changes of information or with the criteria for more effective analysis.

Index

fig. 1 fig. 1 (return text)