History of the Belgian Seismic Stations from 1898

History of the Belgian Seismic Stations from 1898 until now Michel Van Camp 17 February 2005

How measuring an earthquake ? inertial pendulum (same idea since 130 years !) Seismometer Seismogram Seismograph @ 10 km: M = 3 2 µm M = 5 0. 2 mm

Different design of seismometers La. Coste Spring Garden gate Inverted pendulum Leaf spring Bifilar (Zöllner)

Historic : Chang Hêng (132 A. D. ) seismoscope ~2 m

First modern seismographs (1) • XVIII & XIX : First Italian seismoscopes • 1875 : Filippo Cecchi: Seismograph (very low sensitivity : 3 X) • 1887 : First known recording of F. Cecchi

First modern seismographs (2) • XVIII & XIX : First Italian seismoscopes • 1875 : Filippo Cecchi: Seismograph (very low sensitivity) • 1887 : First known recording of F. Cecchi • 1880 : James Ewing : first recording and evaluating the ground movements Pen writing on a black-smoked glass Ewing (1883): “ (1) The very gradual beginning and ending of the disturbance. In none of the observations did the maximum motion occur until after several complete oscillations had taken place. (2) The irregularity of the motion. The successive undulations are widely different both in extent and in periodic time. (3) The large number of undulations in a single earthquake, and the continuous character of the shock. ”’ For the first time, also, seismologists could design their instruments with some knowledge of the phenomena the instruments were to record.

First modern seismographs (3) • XVIII & XIX : First Italian seismoscopes • 1875 : Filippo Cecchi: Seismograph (very low sensitivity) • 1887 : First known recording of F. Cecchi • 1880 : James Ewing : first recording and evaluating the ground movements • 1889 : Ernst von Rebeur-Paschwitz : first teleseism (Japan) recorded in Postdam. Magnification: ~ 100 X • Ca 1900 : first network of seismograph build by J. Ewing, first seismogram bank, application of elastic waves theory to the seismic movements (P, S waves, Earth’s core)

18 February 1898 : request of Ernest Solvay to the Minister Schollaert “Les travaux scientifiques (…) nécessitent, M. le Ministre, une installation souterraine dans un lieu tranquille et protégé, à l’abri des trépidations du sol, et en même temps où l’heure puisse être connue avec une grande précision” “The ROB was the only quiet location in Belgium where accurate time could be provided”

The « Ernest Solvay » station First recording in March 1899 The von Rebeur-Ehlert triple pendulum (museum ORB) Eugène Lagrange (1855 -1936), Professor of physics at the RMS, Corresponding Astronomer at the ROB.

Kafkaian tribulations in 1900 … il fallait recher « un luminaire bien constant, suffisamment intense, d’une fixité aussi grande que possible, dégageant peu de chaleur ou disposé de manière à ce que la chaleur ne put nuire, et pouvant, au minimum, fonctionner quatre jours sans surveillance » . In spite of the authorization from the minister, and payment of the electricity, E. Lagrange and E. Solvay had to wait for 10 months and to exchange 2 dozens of letters with E. Goedseels, « Commissaire du gouvernement administrateur-inspecteur de l’ORB » , to obtain…. Light!

The bulletins

The bulletins (annales de l’ORB >1903) The donation of the Ernest Solvay station to the Belgian State became officially effective on 01 January 1904. (Royal Decree given in Laeken on Novembre 28, 1903 (Moniteur 9/12/1903)

The first pavilion (1898 -1908)

The pavilion (1908)

The early years 1899 -1911 (1) • 21 March 1899: first earthquake recorded in Belgium using the von Rebeur-Ehlert pendulum (? ) • 4 September 1899 : First earthquake officially recorded • 1901 : Lagrange commissioned by J. de Trooz to the permanent seismic commission funded in 1899 and sit in Strasbourg in April 1901. During this meeting E. Lagrange was member of the commission which created the International Association of Seismology (Association Internationale de Sismologie). • 1 st January 1904 : E. Solvay donates the station to Belgium ; Oscar Somville (1880 -1980) is the first head of the seismology service W N-S Alaska (MS = 7. 9) t

The early years 1899 -1911 (2) • June 1906 : installation of 2 horizontal “Bosch-Omori” seismometers (recording on smoked paper drums), magnification ~ 10 X

The early years 1899 -1911 (3) • 1909 : von Rebeur-Ehlert declared obsolete • 1909 : Horizontal Wiechert pendulum (1000 kg) • 1910 : Vertical Wiechert pendulum (1300 kg) • 1911 : Bosch-Omori declared obsolete

Sketch of the Wiechert seismometers © EOST Horizontal components Vertical component Magnification: ~200 X

The early years 1899 -1911 (4) • 1911 : Galitzin horizontal pendulums Bifilar

The control of the instruments

The timing • 1909 : Clock synchronized with the Time Office (daily, ~ 1 s) • 1912 : Continuous synchronization (~ 0. 1 s) • 60 ies: RTB and Neuchâtel (CH) 75 k. Hz synchronization, quartz clocks • 1984 : DCF 77 k. Hz receivers (~ 0. 01 s) • 1998 : GPS receivers (< 0. 001 s)

The other early historical stations : Frameries En 1902, installation of a network to study grisouto-sismic correlation and improve meteorological studies. Stations provided with von Rebeur-Ehlert pendulums, installed by the Société belge de géologie, d’hydrologie et de paléontologie, managed by E. Lagrange. • Frameries (mid-1903) : Agrappe coal mine, Fosse Grand-Trait, 850 m depth, very high risk of firedamp explosion.

The other early historical stations: Quenast • Quenast (fin 1902): porphyry quarry as comparison station outside the coal basin. Uccle could have fulfill this requirement, but « il a paru préférable d’installer une station nouvelle sur un sol considéré comme un des plus stables » . On the other hand, Lagrange wrote: « A sensibilité égale, les déplacements pendulaires en général sont beaucoup moins considérables à Quenast qu’à Uccle; l’agitation sismique due au vent est infiniment moindre à Quenast (…) » « On voit les conduits métalliques peu gracieux, mais nécessaires, que l’aérage de la station nous a amené à installer, pour en assécher autant que possible l’atmosphère intérieure. Si l’œil n’est pas satisfait, le but à atteindre nous forçait à y avoir recours; la buée qui se déposait sur les glaces de l’enregistreur empêchait toute image nette des points lumineux. Que l’esthétique nous pardonne! »

Planed stations (beginning of the XXth century) The time series from Quenast and Frameries were not usable because of the lack of accurate timing, but a correlation between microseismic noise and the weather were observed • Coal mines in Liège • Colfontaine • Coastline (“Mistpoeffers” or « Barisal guns » , ) • Bosch seismometers given to the Ministry of Colonies and sent to Elisabethville (…)

The difficulties « La phase d’installation a réclamé beaucoup de temps, énormément de peines et a eu à surmonter maintes difficultés inattendues qui, toutefois s’aplanissent de jour en jour. A Quenast c’était l’humidité, tellement forte et persistante, qu’il a fallu changer d’emplacement et reconstruire de fond en comble les locaux de la station. A Frameries, dans les profondeurs de la mine grisouteuse, ce furent les recherches relatives à la suppression du danger de l’éclairage électrique (par accumulateurs, à remplacer journellement) qui ont été le principal obstacle à la mise en train et au bon fonctionnement des appareils » Given the problems, this first attempt to establish a seismic network was stopped …

Other historical stations after 1958 • Dourbes-IRM (since 1958) • Warmifontaine (1964 -1970), stopped due to the costs requested by the slate quarry to replace the photographic paper • Luxembourg (1967 -1972), moved to Walferdange • La Gileppe (1968 -1970), moved to Membach

The « cabin » (1962 -1984) Thierry Camelbeeck 1918 -2056 6 channels paper-ink drum recorders + analogue recordings on magnetic tapes

The earthquake of Liège 8 Novembre 1983 at 0 h 49 m (TU) MS = 4. 7 Commune of St Nicolas CHEMINEYS 161 calls 813 interventions (fire brigade) FACADES 211 calls for shoring up 356 shoring up by official services HABITABILITY 93 houses declared as uninhabitable DEMOLITION 15 completely destroyed Thierry Camelbeeck Cost : 1918 -2056 ~ 250 106 EUR

Present instruments

Present Belgian seismic network

Precision in localizing earthquakes Magnitude: Catalogue is complete after 1926 (M>4) 1960 (M>3) 1985 (M>1. 8) Camelbeeck, 1992

Belgian seismologists Oscar Somville 1880 -1980 Eugène Lagrange 1855 -1936 Charles Charlier 1897 -1953 Jean-Marie (as Théo) Van Gils 1918 -1989

Heritage: Protection of historical seismograms Euroseismos project Belgian Science Policy : Digitalization of the scientific and cultural Thierry. Institutes Camelbeeck heritage in the Federal Scientific 1918 -2056

Why studying seismology in Belgium? The seismic network • Monitoring of the seismic activity in our regions: localization, magnitude, … (including the smallest events) • seismic alert with the authorities : localization and impact of the earthquake provided to the Crisis Centrum • Scientific studies on the seismicity in North-western Europe Prevention (seismic hazard) • Instrumental data : Quality of the archives • Historical data : Study of destructive earthquakes since the Middle-age and historical criticism • Geological and paleoseismological data

Cher Thierry, J'ai vu avec intérêt l'annonce de ta conférence et d'un article sur "un siècle de séismologie à l'Observatoire Royal de Belgique". L’histoire du soutien financier d'Ernest Solvay à la station d'Uccle m'a rappelé un détail concernant la station sismologique de Grenoble. En 1903 son directeur Wilfrid Kilian n'arrivait plus à la financer et avait fait appel à la générosité publique. Un donateur anonyme a permis de prolonger la vie de la station jusqu'en 1909. Je pense qu'il pouvait s'agir d'Ernest Solvay car l'appel avait paru dans Ciel et Terre. Avec mes salutations amicales, Julien ---------------------------Julien Fréchet IPGS/EOST, 5 rue René Descartes, F-67084 Strasbourg Cedex Tél. : +33 (0)3 90 24 03 55 frechet@eost. u-strasbg. fr ---------------------------