The 14 August 1708 Manosque, France Earthquake: New Constraints on the Damage Area from In-Depth Historical Studies
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ANNALS OF GEOPHYSICS, VOL. 47, N. 2/3, April/June 2004 The 14 August 1708 Manosque, France earthquake: new constraints on the damage area from in-depth historical studies Grégory Quenet (1), David Baumont (2), Oona Scotti (2) and Agnès Levret (3) (1) Département d’Histoire, Université de Versailles-St-Quentin-en-Yvelines, Guyancourt, France (2) Institut de Radioprotection et de Sûreté Nucléaire, Fontenay-aux-Roses, France (3) Groupe APS, Site de Ruscino, Château-Roussillon, Perpignan, France Abstract In this paper, we re-evaluate the damage area of the 14 August 1708 Manosque earthquake, Southeast France. It is the strongest event (Io = VIII MSK) of a seismic sequence that lasted from March to October 1708. We show that the spatial repartition of the damage that can be proposed based on the existing sources, is clearly biased by the abundant narrative information concerning Manosque. This sparseness in the information can be attributed to differences in communication routes or strategies between the different localities, and affects the global per- ception of the event, especially in the rural area. To tackle this bias, we propose to inventory the building repairs reported in non-narrative sources in order to capture the effects of the Manosque earthquake in the surrounding region. The debates and accounts (between mid-1708 and 1710) show that moderate to heavy repairs consisten- tly affect localities in the epicentral area, covering a region of at least 12 km radius around Manosque. These building repairs, indirectly attesting to earthquake damage, provide valuable and complementary information, which resulted in a better knowledge of this event. In particular, we propose new intensity estimates (I >VI) at six localities. Key words historical earthquakes – non-narrative either no epicentral intensity evaluation is pos- sources – damage area – building repairs sible (50%) or the damage area is only known on the basis of a few observation points (see Scotti et al., this issue). 1. Introduction The 14 August 1708 Manosque earthquake occurred along the Durance fault, southern Fran- The SISFRANCE project aimed to establish ce, the site of a relatively high rate of damaging the most exhaustive intensity and documentary earthquakes (comparable events occurred in database for historical earthquakes felt in Fran- 1509, 1708, 1812, 1913) (fig. 1). It is the stron- ce (Lambert et al., 1997). In spite of the enor- gest event of a seismic sequence that lasted from mous effort that has been made for the past 30 March to October 1708 (http://www.sis years, numerous earthquakes remain for which france.net). In Perrey’s catalogue, dating from the mid 19th century, the Manosque quake was known only through two unreliable secondary Mailing address: Dr. Grégory Quenet, Département sources, giving an incorrect date and mentioning d’Histoire, Université de Versailles-St-Quentin-en-Yveli- nes, 47, boulevard Vauban, 78047 Guyancourt, France; «flames coming out of the ground» (Perrey, e-mail: [email protected] 1845). Vogt (1981; 1993), in the framework of 583 Grégory Quenet, David Baumont, Oona Scotti and Agnès Levret Io VIII VII VI Io 43°48´N 43°42´N 5°36´E 5°42´E 5°48´E 5°54´E Fig. 1. Map showing estimated intensities for the 14 August 1708 Manosque earthquake taken from the SI- SFRANCE database. This event is only known on the basis of a few intensity points. The macroseismic epicentre (star) is located halfway between Manosque and Pierrevert with an epicentral intensity of VIII (fairly well con- strained). Inset: Historical seismicity (Io ≥ VI) and the simplified fault map in the region of the 1708 Manosque earthquake. This region is characterized by a regular moderate seismicity that localizes along the Durance fault. The location of the 1909 Lambesc event on the Trévaresse Fault is also shown as well as the seismicity of the Alpine front to the east. 584 The 14 August 1708 Manosque, France earthquake: new constraints on the damage area from in-depth historical studies SISFRANCE (formerly SIRENE), provided the first luate the effects of the earthquake, especially in historical studies concerning the Durance fault the rural regions, through an in-depth historical events. In 1998, when the research presented in analysis of existing and new documentary sour- this paper started, the sISFRANCE database listed ces. 32 references concerning 18 localities. The da- mage area (I > VI - MSK 1964) was known on the basis of 5 observation points: I = VIII at Ma- 2. An updated hierarchical organization nosque and Pierrevert (quality B, fairly constrai- of the sources ned), I = VII at Corbières and Sainte Tulle and I = VI-VII at Beaumont de Pertuis, (all of quality One of the first difficulties we faced at the C, poorly constrained). The epicentre beginning of this study was the re-appraisal and (Io = VIII) was located roughly midway between tracing of the sources used in previous histori- Manosque and Pierrevert (fig. 1). Although only cal studies. Vogt (1981), for example, who was a few intensity points are available, it is possible the first to work on the Manosque event, used a to roughly estimate the earthquake magnitude at printed edition of the correspondence to the around 5 and its depth at less than 5 km, but with comptroller general of finances (Boislile, a very low level of confidence. 1897). However, the printed edition only provi- In order to increase our confidence in the des an extract of the original, located in the Na- magnitude estimates, in this paper we re-eva- tional Archives (AN Paris, 1708-1709). This Table I. Example of the SISFRANCE referencing scheme for the 14 August 1708, Manosque earthquake (extrac- ted from www.sisfrance.net in 2002). Author Article References Séries Edition Publication date J.P. Rothé Les séismes des Annales 1938, T 3, Mende 1941 Alpes françaises Inst. Physique du géophysi- en 1938 et la séi- Globe de Strasbourg que smicité des Alpes occidentales C. Bernard Essai historique Forcalquier 1904 sur la ville de Forcalquier A. Feraud Histoire civile, Digne 1848 (abbé) politique, religieuse et biographique de Manosque J.B.C. Livre de raison de Inventaire imprimé. Série h 6, Surrach (de) Jean-Baptiste- Arch. Dept. Vaucluse hospice de Charles de Surrach Bédarrides (1706-1754) J.M. Robert Notice historique sur Aix-en- Juillet 1812 le tremblement de Provence terre du village de Beaumont (Vaucluse) 585 Grégory Quenet, Baumont, David Agnès Levret OonaScottiand 586 Fig. 2. Hierarchical tree showing the relation between primary and secondary sources and the bibliography explicitly documenting the 1708 Mano- sque earthquake (recent findings of SISFRANCE and G. Quenet are also included). Architectural elements were added, even if they are not strictly speaking primary sources. For clarity, SISFRANCE is only presented as the starting point of the Manosque studies. References were shortened (see ta- ble of abbreviations in reference list). Most primary sources shown are handwritten documents, among which we highlighted the numerous Mano- sque accounts (box framed). Question marks show that numerous primary sources are still missing. The 14 August 1708 Manosque, France earthquake: new constraints on the damage area from in-depth historical studies original document is much more complete, sin- earthquake on 740 buildings in the city of Ma- ce it contains an additional paragraph, highligh- nosque (including owner’s name, building type, ting the historical context of the text. It also detailed damage, and cost of repairs). contains an unknown letter, used in this study, Thanks to this hierarchical organization, the reporting damage caused by the earthquake in source databank is now available with a consi- the village of Pierrevert. More recently, SI- stent level of exigency but most importantly SFRANCE proposed for this event a list of 32 re- new sources were found, that will allow us to ferences as well as the digitalized copies of the shed new light on the perception of this event. sources (see an extraction in table I). However, the documentary references are not differentia- ted according to their nature. For example, the 3. Analysis of communication to explain Livre de raison de Jean-Baptiste-Charles de the sparse data Surrach (AD Vaucluse, 1706-1754) is a pri- mary source, a material contemporary to the The next step in our study was to interpret Manosque event. On the other hand, the Histoi- each document in its historical context. Indeed, re civile, politique, religieuse et biographique a source is always a trace and never a mirror de Manosque written by Feraud and published from the past (Veyne, 1979) and thus even the in 1848, is a secondary source, which offers an most precise text is biased. To generalize from analysis or a restatement of primary sources. one document to the general effects of an earth- Finally, Rothé (1941) is a seismological study quake and to interpret the non-explicit meaning that belongs to the bibliography, which contains of a source it is necessary to consider the histo- all the studies relying on the documentary sour- rical context. Details of this work were partly ces. Last but not least, systematic referencing of presented in Quenet (2002). the historical seismicity studies is not provided Here we focus the attention of the reader on in SISFRANCE. For example Vogt (1981; 1993) the importance of analysing communication are not referenced, although they quote a manu- routes for a more complete understanding of the script (BM Aix-en-Provence, 18th cent.) that 1708 earthquake. Figure 2 shows that there are was not listed in SISFRANCE at the beginning of many accounts of the 1708 earthquake, which this study. are largely devoted to the city of Manosque. In an attempt to eliminate doubles and to They are long, very similar in style and content, identify new routes of research, Quenet (2002) and appear to be different versions of a single proposed a hierarchical organisation of the sour- manuscript.