Thierry Camelbeeck

Royal Observatory of Belgium · Section of Seismology - Gravimetry

The resurgence of macroseismic data investigations over the last decades has highlighted its importance and versatility in the broader field of seismology. Macroseismic data in Belgium are plenty thanks to systematic and thorough macroseismic surveys, starting from the beginning of the 20 th century. Collection and processing procedures, however, h...

The present study analyses the impact and damage of shallow seismic activity that occurred from the end of the 19th century until the late 20th century in the coal area of the Hainaut province in Belgium. This seismicity is the second-largest source of seismic hazard in north-western Europe after the Lower Rhine Embayment. During this period, five...

La nécessité de mieux connaître et comprendre l’activité sismique dans les régions stables d’Europe est apparue à l’occasion du tremblement de terre de Liège du 8 novembre 1983. Cet événement qui a provoqué des dégâts importants à plus de 17 000 immeubles dans l’agglomération liégeoise a mis en évidence les risques auxquels des séismes, même modéré...

Des études récentes suggèrent que la sismicité dans les régions continentales stables (RCS) et les grands tremblements de terre qui y sont associés peuvent être expliqués par l'action de perturbations transitoires des contraintes locales dans la croûte terrestre ou de la résistance des failles au glissement. Dans cet article, nous expliquons pourqu...

Des études récentes suggèrent que la sismicité dans les régions continentales stables (RCS) et les grands tremblements de terre qui y sont associés peuvent être expliqués par l’action de perturbations transitoires des contraintes locales dans la croûte terrestre ou de la résistance des failles au glissement. Dans cet article, nous expliquons pourqu...

Icequakes are the result of processes occurring within the ice mass or between the ice and its environment. Studying icequakes provides a unique view on ice dynamics, specifically on the basal conditions. Changes in conditions due to environmental or climate changes are reflected in icequakes. Counting and characterizing icequakes is thus essential...

Shallow, light to moderate magnitude earthquakes in stable continental regions can have a damaging impact on vulnerable surface constructions. In the coal area of the Hainaut province in Belgium, a century of shallow seismic activity occurred from the end of the 19th century until the late 20th century. This seismicity is the second largest source...

We present a comprehensive study of the 23 February 1828 earthquake that caused severe damage in the central part of the present Belgian territory. We synthesised and critically reassessed the information provided by contemporaneous scientific studies and newspapers of the Low Countries. In addition, a systematic survey of official, private, and re...

Icequakes are the result of processes occurring within the ice mass, or between the ice and its environment. Studying icequakes provide a unique view on the ice dynamics, specifically on the basal conditions. Changes in conditions due to environmental, or climate, changes, are reflected in icequakes. Counting and characterizing icequakes is thus es...

Broken or deformed speleothems have been used as indicators of paleo-earthquakes since the 1990s; however, a causal link is difficult to prove except for some thin speleothems. In contrast, the presence of intact speleothems permits estimating an upper limit of the level of horizontal ground motions of past seismicity in the area. The natural frequ...

Since the 14 th century, moderate seismic activity with 14 earthquakes of magnitude Mw≥5.0 occurred in Western Europe in a region extending from the Lower Rhine Graben (LRG) to the southern North Sea. In this paper, we investigate how well this seismic activity could reflect that of the future. The observed earthquake activity in the LRG is continu...

We report on a pilot demonstration of the usefulness of analog seismograms to improve the database of ocean storms before the 1980s by providing additional data for the quantitative validation of ocean wave modeling, in particular for extreme events. We present a method for automatic digitization of paper seismograms to extract microseismic ground-...

Despite the real societal challenge posed by their important potential of destruction, the causes of infrequent moderate and large earthquakes in tectonically stable continental regions (SCR) are not yet well understood. Nevertheless, recent studies suggest that large earthquakes in SCR can be explained by transient perturbations of local crustal s...

Owing to the implantation of the « Princess Elisabeth » polar base in East-Antarctica, the Royal Observatory of Belgium undertook research in seismology by installing in February 2010 a permanent broadband seismic station on the bedrock near the base. Due to the poor coverage of permanent seismic stations in Antarctica and the small number build on...

Data and metadata products based on intensive terrestrial gravity measurements covering the Belgian territory have been established compliant to the new ISO19115‐1 profile for gravity‐related data. A short historical introduction on gravity measurements on the Belgian territory is presented, starting with the first gravity measurement in 1892. This...

Over a year of seismic observations, ~5000 short duration icequakes were detected by a permanent broadband station installed at the Princess Elisabeth base, located ~180 km inland in eastern Dronning Maud Land, East-Antarctica. Icequake detection via seismic waveform pattern recognition indicates the presence of two dominating clusters of events, t...

Acquiring and building Digital Outcrop Models (DOM) becomes an essential approach in geosciences. This study highlights the strong potential of Structure-from-motion (SfM) photogrammetry for full-3D mapping of inaccessible outcrops, combining pictures captured from field and from unmanned aerial vehicle-embedded digital cameras. We present a workfl...

Prominent landforms, either buried or preserved at the seafloor, provide important constraints on the processes that led to the opening and present-day configuration of the Dover Strait. Here, we extend previous investigations on two distinct landform features, the Fosse Dangeard and Lobourg Channel, to better understand the poly-phase history of t...

The aim of this paper is to propose the creation, in terms of European Macroseismic Scale (EMS-98), of the entire macroseismic field of the 6 May 1976 Friuli earthquake. Only forty odd years have passed, and nothwithstanding that there is a huge quantity of existing data, it was still disturbing to find that much of the original data are missing an...

Tectonic landforms are generally modest in stable plate interiors characterized by low strain rates and rare earthquakes. Nevertheless, specific investigations identified such landforms in Belgium, which is located in the most seismically active region of stable Europe northwest of the Alps. Here, we present two active fault zones among the best do...

https://presentations.copernicus.org/EGU2018-1214_presentation.pdf

Collapse activation is an ongoing process in the evolution of karstic networks related to the weakening of cave vaults. Because collapses are infrequent, few have been directly observed, making it challenging to evaluate the role of external processes in their initiation and triggering. Here, we study the two most recent collapses in the Dôme chamb...

Why recent large earthquakes caused shaking stronger than shown on earthquake hazard maps for common return periods is under debate. Explanations include: (1) Current probabilistic seismic hazard analysis (PSHA) is deficient. (2) PSHA is fine but some map parameters are wrong. (3) Low-probability events consistent with a map sometimes occur. This i...

We recently discovered in the regional record office of North Rhine-Westphalia (Landesarchiv Nordrhein Westfalen) in Duisburg (Germany) numerous original documents organized and distributed during the nineteenth century by the Prussian authority. These documents constitute a series of completed surveys very similar to present-day macroseismic quest...

The online collection of earthquake reports in Europe is strongly fragmented across numerous seismological agencies. In this contribution we demonstrate how merging online institutional macroseismic data can improve the density of observations and the quality of intensity shaking maps. Instead of using ZIP code maps, we geocode individual response...

Late Quaternary separation of Britain from mainland Europe is considered to be a consequence of spillover of a large proglacial lake in the Southern North Sea basin. Lake spillover is inferred to have caused breaching of a rock ridge at the Dover Strait, although this hypothesis remains untested. Here we show that opening of the Strait involved at...

Supplementary Figures and Supplementary Tables

In this work, we present the result of a large-scale geophysical survey that had the objective of identifying the subsurface characteristics and the NE–SW extension of the Hockai Fault Zone: a major NNW–SSE oriented crustal-rooted fault zone crossing the Stavelot-Venn Massif (Eastern Belgium). 31 two-dimensional electrical resistivity tomography (E...

The online collection of earthquake reports in Europe is strongly fragmented across numerous seismological agencies. This paper demonstrates how collecting and merging online institutional macroseismic data strongly improves the density of observations and the quality of intensity shaking maps. Instead of using ZIP code Community Internet Intensity...

Our knowledge about large earthquakes in stable continental regions comes from studies of faults that generated historical surface rupturing earthquakes or were identified by their recent imprint in the morphology. Here, we evaluate the co-seismic character and movement history of the Rauw fault in Belgium, which lacks geomorphological expression a...

In the US, the USGS is the only institute that gathers macroseismic data through its online “Did You Feel It?” (DYFI) system allowing a homogeneous and consistent intensity assessment. In Europe, however, we face a much more complicated situation. As almost every nation has its own inquiry in their national language(s) and both the EMSC and the USG...

The online collection of earthquake testimonies in Europe is strongly fragmented across numerous seismological agencies. This paper demonstrates how collecting and merging “Did You Feel It?” (DYFI) institutional macroseismic data strongly improves the quality of real-time intensity maps. Instead of using ZIP code Community Internet Intensity Maps w...

In probabilistic seismic-hazard assessment for stable continental regions (SCRs), the maximum magnitude Mmax truncating the earthquake magnitude–frequency distribution is commonly based on Bayesian updating of a global prior distribution derived from the distribution of observed Mmax in superdomains (groups of tectonically similar domains). We use...

Large earthquakes within stable continental regions (SCR) show that significant amounts of elastic strain can be released on geological structures far from plate boundary faults, where the vast majority of the Earth's seismic activity takes place. SCR earthquakes show spatial and temporal patterns that differ from those at plate boundaries and occu...

In Antarctica, locally grounded ice, such as ice rises bordering floating ice shelves, plays a major role in the ice mass balance as it stabilizes the ice sheet flow from the hinterland. When in direct contact with the ocean, the ice rise buttressing effect may be altered in response of changing ocean forcing. To investigate this vulnerable zone, f...

Since 2009, we have installed five GNSS stations around the Princess Elisabeth Base in Antarctica. Four stations have been installed on stable bedrock, while the fifth station is installed at the Derwael Ice rise. The stations are used in the frame of the BELSPO projects, GIANT-LISSA and IceCon, to provide information for monitoring the horizontal...

On 3 December 1828 at half past six in the evening, the border region between Belgium and Germany was stricken by a moderate earthquake. Up to now, the available information on this event has been essentially provided by a few contemporaneous scientific studies. To better evaluate its impact, location and magnitude, we have searched for new origina...

Since 1938, when an earthquake occurs, the Royal Observatory of Belgium (ROB) sends out national earthquake inquiries to each municipality to create intensity maps of the felt area. Since 2002, only few hours after the ML 4.9 Alsdorf earthquake, the paper inquiry was complemented by an online “Did You Feel It?” (DYFI?) inquiry on the seismology.be...

Intraplate seismicity is often characterized by episodic, clustered and migrating earthquakes and extended after-shock sequences. Can these observations – primarily from North America, China and Australia – usefully be applied to seismic hazard assessment for intraplate Europe? Existing assessments are based on instrumental and historical seismicit...

The assumed magnitude of the largest future earthquakes, Mmax, is crucial in assessing seismic hazard, especially for critical facilities like nuclear power plants. Absent any theoretical basis, estimates are made using various methods and often prove far too low, as for the 2011 Tohoku, Japan, earthquake. Estimating Mmax is particularly challengin...

The region of Court-Saint-Etienne, a community at about 20 km SE of Brussels in Walloon Brabant, has experienced a seismic sequence from 12 July 2008 to 18 January 2010. This seismic sequence is characterised by several periods of swarm activity, of which the largest swarm activity took place in the summer of 2008 and spring 2009, alternating with...

Two different ambient seismic noise techniques allow the determination of velocity models at Ijen caldera and Kawah Ijen volcano. At Ijen caldera, two average velocity models are constrained down to a depth of 3 km by inverting the stacked dispersion curve obtained by ambient noise cross-correlation. In addition, four local velocity models were obt...

On 1580 April 6 one of the most destructive earthquakes of northwestern Europe took place in the Dover Strait (Pas de Calais). The epicentre of this seismic event, the magnitude of which is estimated to have been about 6.0, has been located in the offshore continuation of the North Artois shear zone, a major Variscan tectonic structure that travers...

Structural interpretations of the tectonic grain of orogenic mountain belts have often been based on the study of potential field data. The steep architecture of mountain belts can be highlighted by the inclination of the magnetic field and by the persistence of aeromagnetic lineaments with depth. With respect to seismology, matched filtering has p...

Since 2010, the Kawah Ijen volcano has been equipped with seismometers and its extremely acid volcanic lake has been monitored using temperature and levelling sensors, providing unprecedented time resolution of multi-parametric data for an acidic volcanic lake. The nature of stress and mass changes of the volcano is studied by combining seismic ana...

Kawah Ijen is a composite volcano located at the easternmost part of Java island in Indonesia and hosts the largest natural acidic lake in the world. We have gathered all available historical reports on Kawah Ijen’s activity since 1770 with the purpose of reviewing the temporal evolution of its activity. Most of these observations and studies have...

In order to monitor the hydrological strain forces of the karst micro fissure networks and local fault activities, six capacitive extensometers were installed inside a karstic cave near the midi-fault in Belgium. From 2004 to 2008, the nearby Lomme River experienced several heavy rains, leading to flooding inside the Rochefort cave. The highest wat...

We present results of our study aimed at understanding the dynamics of fluids inside a “wet” volcano through the analysis of swarms of long-period (LP) events accompanying the 2011 seismic unrest at Papandayan volcano, West Java, Indonesia. Prior to this unrest, we measured an extremely high percentage (100%) of CO2 in the ground at the summit crat...

Estimating Mmax, the assumed magnitude of the largest future earthquakes expected on a fault or in an area, involves large uncertainties. No theoretical basis exists to infer Mmax because even where we know the long-term rate of motion across a plate boundary fault, or the deformation rate across an intraplate zone, neither predict how strain will...

Defining area or fault sources to assess seismic hazard is a difficult and often subjective task in low-seismicity regions. Smoothed or gridded seismicity is a method that has been developed to derive the spatial seismicity pattern in a more objective way, based only on known seismicity and not requiring assumption of source geometries. Smoothed se...

Intraplate earthquakes occur away from tectonic plate boundaries: their locations are difficult to predict, risking huge damage and loss of life. The 2001 Bhuj earthquake (featured in this book) was the largest intraplate earthquake for three decades and has provided unique insight into these events. This cutting-edge book brings together research...

We first provide a brief overview of the evolution of seismic hazard assessment in Belgium, followed by a comparison of the current official seismic hazard map used to define the seismic zonation of Belgium in the framework of Eurocode-8 with the corresponding map from the European SHARE project. The general pattern of the PGA spatial distribution...

Between 2008 and 2010, the Royal Observatory of Belgium received numerous ‘Did You Feel It’-reports related to a 2-year lasting earthquake swarm at Court-Saint-Etienne, a small town in a hilly area 20 km SE of Brussels, Belgium. These small-magnitude events (-0.7 ≤ ML ≤ 3.2, n = c. 300 events) were recorded both by the permanent seismometer network...