Major Rockfall Research Articles

CHALCOLITHIC/EARLY BRONZE AGE AND ADDITIONAL MAGDALENIAN RADIOCARBON DATES FOR EL MIRÓN CAVE (RAMALES DE LA VICTORIA, CANTABRIA, SPAIN). DATE LIST VII

ABSTRACTThere are now 101 radiocarbon dates from the long Paleolithic and post-Paleolithic culture-stratigraphic sequence in El Mirón Cave, Cantabrian Spain. Here we report on two dates on bone from two different humans whose remains were found in disturbed surface sediments in the cave vestibule rear and that confirm the existence of burials in addition to previously reported residential occupations in the vestibule front pertaining to the Chalcolithic and early Bronze Age periods (ca. 5500–3500 cal BP). In another attempt to resolve problems of stratigraphic incoherence of dates from the early Magdalenian periods in the vestibule rear, six new assays on faunal remains from Levels 119, 117, 114, 108, and 106 were run at Queen’s University in Belfast. There continue to be date inversions in the Lower Magdalenian range of levels that may be explained by a combination of intensive anthropic and rodent activity, major rock fall, slope wash and gravity-caused object movements, as well as possible problems in following some thin levels during excavations over a large area and across many years of work in the cave vestibule interior, particularly in the absence of any layers that are culturally sterile or even poor. Nonetheless, the coherent age of the Initial Magdalenian is fully confirmed by a new date from Level 21 in the vestibule front at ca. 22,000–20,500 cal BP), as is the general age range of the Lower Magdalenian (ca. 20,500–18,000 cal BP).

Direct dating of a major rockfall at the Ba'ja Neolithic site (Jordan) using rock surface luminescence

In this study, we use luminescence rock surface dating to provide burial ages for buried surfaces of a large boulder now positioned on top of the ruins of the Neolithic Ba'ja village in Southern Jordan. Luminescence depth profiles for quartz optically stimulated luminescence (OSL), and feldspar infrared stimulated luminescence (IR50) signals indicate that the boulder experienced a complex transport history of at least two exposure and two burial events before final emplacement. By comparing the fading-corrected feldspar IR luminescence burial ages derived from these rock surfaces with quartz OSL ages derived from sediment infill from the archaeological structures underneath the boulder, it is concluded that there was a rockfall event around 7–8 ka ago, possibly as the result of an earthquake. Whatever the nature of this event, it resulted in the first recorded movement of the boulder, when the rock was presumably dislodged on the hill slope but did not travel all the way to the settlement at the foot of the slope. About 3–4 ka ago, after the village had been abandoned and the rooms filled with rubble, further movement occurred, possibly initiated by an earthquake. This final transport event moved the boulder further downslope, embedding it in the cultural layers of the derelict settlement on top of the partially collapsed settlement walls.

The three-stage rock failure dynamics of the Drus (Mont Blanc massif, France) since the June 2005 large event

Since the end of the Little Ice Age, the west face of the Drus (Mont Blanc massif, France) has been affected by a retrogressive erosion dynamic marked by large rockfall events. From the 1950s onwards, the rock failure frequency gradually increased until the large rockfall event (292,680 m3) of June 2005, which made the Bonatti Pillar disappear. Aiming to characterize the rock failure activity following this major event, which may be related to permafrost warming, the granitic rock face was scanned each autumn between October 2005 and September 2016 using medium- and long-range terrestrial laser scanners. All the point clouds were successively compared to establish a rockfall source inventory and determine a volume-frequency relationship. Eleven years of monitoring revealed a phase of rock failure activity decay until September 2008, a destabilization phase between September 2008 and November 2011, and a new phase of rock failure activity decay from November 2011 to September 2016. The destabilization phase was marked by three major rockfall events covering a total volume of 61,494 m3, resulting in the progressive collapse of a new pillar located in the northern part of the June 2005 rockfall scar. In the same way as for the Bonatti Pillar, rock failure instability propagated upward with increasing volumes. In addition to these major events, 304 rockfall sources ranging from 0.002 to 476 m3 were detected between 2005 and 2016. The temporal evolution of rock failure activity reveals that after a major event, the number of rockfall sources and the eroded volume both follow a rapid decrease. The rock failure activity is characterized by an exponential decay during the period following the major event and by a power-law decay for the eroded volume. The power law describing the distribution of the source volumes detected between 2005 and 2016 indicates an exponent of 0.48 and an average rock failure activity larger of more than six events larger than 1 m3 per year. Over the 1905–2016 period, a total of 426,611 m3 of rock collapsed from the Drus west face, indicating a very high rock wall retreat rate of 14.4 mm year−1 over a surface of 266,700 m2. Averaged over a time window of 1000 years, the long-term retreat rate derived from the frequency density integration of rock failure volumes is 2.9 mm year−1. Despite difficulty in accessing and monitoring the site, our study demonstrates that long-term surveys of high-elevation rock faces are possible and provide valuable information that helps improve our understanding of landscape evolution in mountainous settings subject to permafrost warming.

The Seismic Factor in the Excitation of Endogenous and Exogenous Processes on Klyuchevskoi Volcano, Kamchatka

The Klyuchevskoi stratovolcano is one of the largest and most active volcanoes in the world; changes of varying sizes have affected the morphology of its surface during historical time. These rock failures mostly occur in long-lived geologic features, namely, volcano-tectonic chutes. Several researchers have made forecasts of failures based on the relief and morphology of the volcano, the system of tectonic discontinuities within its edifice, the localization of parasitic eruptions, the emplacement of intrusions and dikes that have dissected the edifice, glacier activity on the slopes, and other factors. The part played by seismic activity in the preparation and occurrence of major rockfalls and landslides on the volcano has not been previously studied in its own right. The present paper contains an analysis of Klyuchevskoi seismicity related to eruption periods as a key factor to induce deformation and major rockfalls and landslides due to various causes. According to the spatial distribution of earthquakes and the associated seismic energy, the northwestern and southeastern sectors of the volcano are prone to major collapses. This appears to be due to an extension of the edifice in relation to a north-northeast striking fault that traverses the edifice.

A multi-method monitoring of timing, magnitude and origin of rockfall activity in the Japanese Alps

A multi-method monitoring was conducted to detect the timing and trigger of rockfall activity on an alpine rockslide cliff composed of Cretaceous sandstone and shale in the southern Japanese Alps (Aresawa rockslide, 2900 m above sea level). The monitoring programme includes manual measurements of flaking from painted rock surface and collection of fallen debris, daily time-lapse imaging of the rockwall, automated recordings of rock temperature, rock moisture and influencing meteorological factors (air temperature and precipitation). A stereographic pair of sequential photographs is used to visually identify the location of new erosion and semi-quantitative evaluation of detached materials at daily resolution. Six years (2010–2016) of debris trapping show major rockfall activity in winter (between November and May) and occasional activity associated with heavy rains in summer, and yield an average rate of rockwall retreat on the order of 1 mm a−1. The rockwall shows heterogeneous debris production mainly reflecting joint spacing. Time-lapse imaging displays at least 10–15 rockfall events per year within the shot area (~500 m2). The integration of multiple data suggests at least five types of triggering processes towards rockfalls, which recur annually. (1) In summer and early autumn, heavy rainfalls raise the moisture content of the shallow bedrock, often triggering significant rockfalls, probably due to raised water pressure in rock joints or lubrication of joints. (2) In late autumn and late spring, light or intermediate rainfalls are sometimes followed by high moisture, shallow freezing, rapid thawing and eventually by different scales of rockfalls. (3) In winter and early spring, the same process as in the second case, but rainfall is replaced by snowfall, triggers submeter-scale rockfalls. (4) Deep seasonal freezing to about 5 m enables release of meter-scale rockfalls during seasonal thawing periods from late spring to early summer. (5) Short-term large thermal fluctuations that produce cyclic thermal stress may also contribute to submeter-scale rockfalls, mainly in winter locally enhanced by freeze-thaw action.

Newspaper reporting of the April 2007 eruption of Piton de la Fournaise part 1: useful information or tabloid sensationalism?

During March, April and May 2007 the local newspaper for the island of La Réunion, “Le Journal de L’Ile de La Réunion” (JIR), published 427 articles relating to natural hazards, with hazard-related articles occupying a total paper area of 21.94 m2 and appearing in all but four of the 90 editions of the newspaper. This high level of coverage was due to the passage of two cyclones in March, the largest historical eruption of Piton de la Fournaise in April, and a major rock fall event in May. The high level of coverage may also be due to the fact that JIR is a tabloid that follows tabloid news values. Cyclones, volcanic eruptions and rock falls fit the news values of a tabloid well, especially when the stories involve the power elite, feature stories of human interest, include surprise elements and rescues, and are of high impact, especially to the local population. Disasters also provide spectacular imagery and the opportunity for eye-catching headlines, which is another element of the tabloid format. These key parameters thus all flag stories about natural hazards and, in particular, volcanic eruptions as being newsworthy for a tabloid.Of the page space devoted to natural hazards, 9.24 m2 (42%) were set aside to reporting of volcanic activity, specifically the April 2007 eruption of Piton de la Fournaise. We completed a content analysis of these reports to understand the quality of information disseminated to the readership and to extract data regarding the impact of the eruption on local communities. We found the information to be of extremely high quality, with lava reporting being the most important issue covered by page area, mostly due to its photogenic nature. If we consider text-dominated reports, and exclude photo-montages, then the order of importance in terms of space set aside to reporting of a particular theme becomes: (i) general eruption details; (ii) summit collapse; (iii) lava flows; (iv) evacuation; (v) gas; (vi) ocean-entry; (v) air fall; (vi) vegetation fires (lit by lava contact); and (vii) volcano-seismicity. As the eruption and the nature of the hazard evolved (from lava flow through air-fall and gas, to summit collapse and ocean-entry) so too did the focus of the reporting. Once the eruption had finished, emphasis shifted from the hardships of the impacted community to sightseeing and tourism. We found that the quality of the reporting resulted from the use of journalists who were specialized in their reporting areas and who therefore knew the background and the correct sources to seek out for information. This shows that a well-informed journalist can be (i) a means to disseminate information and educate an impacted population, and (ii) a source of information for the volcanologist regarding societal impacts of, and population responses to, natural hazards.

Slope, Scarp and Sea Cliff Instability Susceptibility Mapping for Planning Regulations in Almada County, Portugal

In Portugal, the modifications introduced in 2008 and 2012 in the National Ecological Reserve law (REN) included the mandatory study of slope instability, including slopes, natural scarps, and sea cliffs, at municipal or regional scale, with the purpose of avoiding the use of hazardous zones with buildings and other structures. The law also indicates specific methods to perform these studies, with different approaches for slope instability, natural scarps and sea cliffs. The methods used to produce the maps required by REN law, with modifications and improvements to the law specified methods, were applied to the 71 km2 territory of Almada County, and included: 1) Slope instability mapping using the statistically based Information Value method validated with the landslide inventory using ROC curves, which provided an AAC=0.964, with the higher susceptibility zones which cover at least 80% of the landslides of the inventory to be included in REN map. The map was object of a generalization process to overcome the inconveniences of the use of a pixel based approach. 2) Natural scarp mapping including setback areas near the top, defined according to the law and setback areas near the toe defined by the application of the shadow angle calibrated with the major rockfalls which occurred in the study area; 3) Sea cliffs mapping including two levels of setback zones near the top, and one setback zone at the cliffs toe, which were based on systematic inventories of cliff failures occurred between 1947 and 2010 in a large scale regional littoral monitoring project. In the paper are described the methods used and the results obtained in this study, which correspond to the final maps of areas to include in REN. The results obtained in this study may be considered as an example of good practice of the municipal authorities in terms of solid, technical and scientifically supported regulation definitions, hazard prevention and safe and sustainable land use management.

Brief communication: 3-D reconstruction of a collapsed rock pillar from Web-retrieved images and terrestrial lidar data – the 2005 event of the west face of the Drus (Mont Blanc massif)

Abstract. In June 2005, a series of major rockfall events completely wiped out the Bonatti Pillar located in the legendary Drus west face (Mont Blanc massif, France). Terrestrial lidar scans of the west face were acquired after this event, but no pre-event point cloud is available. Thus, in order to reconstruct the volume and the shape of the collapsed blocks, a 3-D model has been built using photogrammetry (structure-from-motion (SfM) algorithms) based on 30 pictures collected on the Web. All these pictures were taken between September 2003 and May 2005. We then reconstructed the shape and volume of the fallen compartment by comparing the SfM model with terrestrial lidar data acquired in October 2005 and November 2011. The volume is calculated to 292 680 m3 (±5.6 %). This result is close to the value previously assessed by Ravanel and Deline (2008) for this same rock avalanche (265 000 ± 10 000 m3). The difference between these two estimations can be explained by the rounded shape of the volume determined by photogrammetry, which may lead to a volume overestimation. However it is not excluded that the volume calculated by Ravanel and Deline (2008) is slightly underestimated, the thickness of the blocks having been assessed manually from historical photographs.

Forecasting rock slope failure: how reliable and effective are warning systems?

Warning systems are increasingly applied to reduce damage caused by different magnitudes of rockslides and rockfalls. In an integrated risk-management approach, the optimal risk mitigation strategy is identified by comparing the achieved effectiveness and cost; estimating the reliability of the warning system is the basis for such considerations. Here, we calculate the reliability and effectiveness of the warning system installed in Preonzo prior to a major rockfall in May 2012. “Reliability” is defined as the ability of the warning system to forecast the hazard event and to prevent damage. To be cost-effective, the warning system should forecast an event with a limited number of false alarms to avoid unnecessary costs for intervention measures. The analysis shows that to be reliable, warning systems should be designed as fail-safe constructions. They should incorporate components with low failure probabilities, high redundancy, have low warning thresholds, and additional control systems. In addition, the experts operating the warning system should have limited risk tolerance. In an additional hypothetical probabilistic analysis, we investigate the effect of the risk attitude of the decision makers and of the number of sensors on the probability of detecting the event and initiating a timely evacuation, as well as on the related intervention cost. The analysis demonstrates that quantitative assessments can support the identification of optimal warning system designs and decision criteria.

Strong proximal earthquakes revealed by cosmogenic 3He dating of prehistoric rockfalls, Christchurch, New Zealand

The 2011 rupture of previously undetected blind faults beneath Christchurch, New Zealand, in moment magnitude (M w ) 6.2 and 6.0 earthquakes triggered major rockfalls that caused fatalities and infrastructure damage. Here we use field, geospatial, seismologic, numerical modeling, and cosmogenic 3 He data to provide first evidence for prehistoric rockfall ca. 8– 6 ka, and a possible preceding event ca. 14– 13 ka, at a site where extensive rockfall occurred in the Christchurch earthquakes. The long (∼7 ± 1 k.y.) time intervals between successive rockfall events and the high peak ground velocity thresholds required for rockfall initiation at this site (∼20–30 cm/s) preclude earthquakes from major identified seismic sources, including the plate boundary Alpine fault, as likely rockfall triggering sources. Rockfalls were probably triggered by strong paleoearthquakes sourced from active faults proximal (i.e., <10–20 km) to Christchurch, including the sources of the 2011 Christchurch earthquakes and/or other currently unidentified faults. Given the inherent incompleteness of seismic source catalogues and challenges in obtaining earthquake chronologies for blind faults, high scientific priority should be given to the search for, and analysis of, geologic records of strong earthquake shaking near populated areas.

Datations 36Cl de la fermeture de la grotte Chauvet, implications géomorphologiques et archéologiques

The chauvet cave discovery in 1994 has challenged our archeological, art and chronological benchmarks previously admitted and based on the chronological stylistic framework. The aim of this study is dating of the major rockfalls, which have closed the Chauvet cave to the human and animals. This work shows the results of the geomorphological approach combining high-resolution topographic survey (terrestrial LiDAR) and cosmogenic dating. The rockfall scars and rockfall deposit 3D analysis has permitted to reconstruct the Chauvet cave paleo entrance. The rock sampling strategy is based on the existence of three rockfall scars on the rockwall overhanging the Chauvet cave. All the 36Cl production factor was considered and both of them are derived from the 3D topographic. These results allow establishing a coherent and absolute chronological framework of the Chauvet cave entrance for 34,000 years until its definitively and sudden closure there 22, 000 years.

Quantifying the protective function of a forest against rockfall for past, present and future scenarios using two modelling approaches

Following a major rockfall event in 1987, two types of protection measures were taken in the village Saint Martin le Vinoux (French Alps). Firstly, technical measures using civil engineering were installed, and secondly, a forest management intervention to increase its protection was carried out. This study aims to assess whether this intervention was successful in the sense that it improved the protective function of the forest. We evaluated the rockfall risk for the situation of 1987 (before the intervention), today and the future, using model simulations with past, present and future vegetation cover scenarios. To increase the meaningfulness of our results, we used two different models, called Rockfor.NET, which is a rapid one-dimensional rockfall forest evaluation tool, using simple slope and forest characteristics and RockyFor, a process based on three-dimensional rockfall simulation model that takes the barrier effect of individual trees explicitly into account. Both models correctly predicted that the forest was not capable of stopping rocks from the 1987 rockfall event. Further, both models indicate an increase of the number of rocks reaching the base of the slope from 1987 onwards. RockyFor shows an increase from 11% in 1987 to 19% in 2086. Rockfor.NET shows an increase from 26% in 1987 to 56% in 2086. We conclude that a second attempt to increase the protective function of the forest should aim at restoring a dense coppice stand.

Rapid lake infill following major rockfall (bergsturz) events revealed by ground-penetrating radar (GPR) measurements, Reintal, German Alps

The capability of GPR (ground-penetrating radar) measurements to decipher the sedimentary history of young alluvial plains is investigated. The sediment basins result from the infill of two lakes, which were dammed by high-magnitude rockfalls 400—600 and 200 years ago in an Alpine trough valley. The thickness and structure of the dammed sediments was derived from a series of longitudinal and cross profiles. In order to take advantage of both high penetration and high resolution measurements, we applied 25, 50, 100 and 200 MHz antennas. The radargrams allow for a detailed analysis of the history of the alluvial fill. The pre-existing valley bottom is clearly visible under one of the basins. The profiles display the former clayey lake bottom and illustrate several stages of lake infill. Small-scale sedimentary structures, such as topset beds or foreset beds, are discernible and provide proxy information on water level, sediment supply and phases of infill activity. At the second basin, discordant structures in the adjacent sediment cones indicate the abrupt rise of the base level resulting from the rockfall event. Radar-derived information and historical records of lake retreat were used to reconstruct the sediment budget of the 200 year lifespan of the younger alluvial plane. Therefore, it can be concluded that the sedimentation rates of the twentieth century (489 ± 87 m3/yr) are several times larger than those of the nineteenth century (103 ± 7 m3/yr). A 130-yr rainstorm record suggests that the overall increase in sediment supply in the twentieth century corresponds to increased rainstorm frequencies during warm periods.

Prédisposition, préparation et déclenchement des mouvements de versant

ABSTRACT Rock slope movements can be considered, from a mechanical standpoint, as the consequence of predisposition, preparation and trigger factors. In the case study of the “Rochers de Valabres” slope (Southern French Alps), which experienced major rockfalls in 2000 and 2004, these factors are analysed by means of field observations, high-precision geodetic monitoring and acoustic emissions monitoring, as well as by numerical modelling. This paper places special emphasis on the role of both the fracture network and thermal effects.

Instabilities in the summit region of Mount Etna during the 1999 eruption

During the 1999 eruption of Mount Etna, Sicily, the summit of the volcano changed dramatically. Lavas erupted from a fissure on the southern flank of SE Cone formed a large compound flow field that buried a substantial part of the northern wall of Valle del Bove and the ground between there and SE Cone. Hot mass flow deposits formed on the eastern and western flanks of the Chasm following a period of intense Strombolian activity. At the same time, a new vent opened on the southern flank of SE Cone and there was a major rockfall from its summit. Seven weeks later, part of the outer western rim of Bocca Nuova crater collapsed during another period of intense Strombolian activity, and lava emerged at a high effusion rate through the breached crater wall. Following a subsequent collapse of the Bocca Nuova crater rim, a hot avalanche flowed a few hundred metres on top of the previous lava flow field. Similar deposits have been described on other volcanoes, but their importance in the evolution of the summit of Etna has not previously been recognised.

The 1998 Tatopani Landslide in the Kali Gandaki Valley of Western Nepal: cause and relation to mass rock creep

The village of Tatopani lies on a small gravel terrace in the middle reach of the Kali Gandaki River, along a narrow course of about 2 km in length. One kilometre south of the village, a major rockfall occurred recently in the region of the Lesser Himalaya, which is built up of low-grade metamorphic rocks of the Kuncha Group, consisting of a thick sequence of foliated phyllites and bedded quartzites as well as interlayering of both lithologies. The monoclinal structure of these metasedimentary rocks is clearly related to the general trend of the Nepal Himalaya near the Main Central Thrust (MCT): strike NW-SE 140- 150°, dip 25-45° NE. Besides a clear foliation in the phyllites (s1) parallel to the quartzite bedding (s0), four other discontinuities are also developed as steep joints (j1-j4).&#x0D; Two joint sets j1 and j2, both crossing each other and both acting in conjunction with the foliation (s1) as a shear plane, were responsible for the wedge failure of the Tatopani Landslide, which led to a rockfall and avalanche of about 400,000 cubic metres and dammed the river for about 72 hours. It is noteworthy that several other - strikingly similar but older - weathered wedge failure surfaces are exposed at various spots all over the same ridge, which is the spur-ridge dividing the Kali Gandaki River from the Gar Khela tributary. This visible slope instability evidenced by relatively small wedge failures is causally connected with a much larger mechanism, namely mass rock creep or "sagging"- a purely gravitational slope deformation. The repeatedly occurring wedge failures producing landslides (rockfalls and rock avalanches) are caused by extreme shear stress and deep-reaching joints and fissures during mass rock creep. Only the final trigger for landslides or rockfalls is provided by extreme and lengthy monsoon rainstorms, which reinforce the cleft-water pressure inside rock discontinuities and openings, especially along the impermeable interface of quartzites and phyllites (s0 =s1) at the base of the wedge failure.&#x0D; The right (western) bank above the village is morpho-dynamically active also through mass rock creep and “pushes” laterally against the river course. However, the kinematics of the rock slope is rather different because the foliation geometry is more important. The foliation dips obliquely towards the riverside and consequently has facilitated extremely slow large­ scale dip slope movements along quartzite-phyllite interfaces (s0) without any catastrophic danger. However, the creeping slope movements of thick quartzite: members caused a set of conjugate extension faults producing toppling at the distal slope margins.&#x0D; Rock avalanches from the spur-ridge on the eastern (left) bank of the Kali Gandaki River S of Tatopani will always remain a threat, especially when excessive seasonal rains increase the cleftwater pressure inside the invisibly slow creeping system of the steep bank in an extraordinary manner.

Dating San Andreas fault earthquakes with lichenometry

RegionalrockfalleventsintheSierraNevadaofCaliforniaare caused by distant earthquakes on the northern and southern San Andreasfaultaswellasbylocalearthquakes.Lichenometricdating of synchronous pulses of rockfalls that are presumed to be caused by five historical earthquakes suggests an accuracy of 2.2‐3.5 yr (95% confidence level) for dating young events. Comparison of lichenometric ages for prehistorical rockfalls with precise radiocarbon ages of surface-rupture times at the Pallett Creek and Wrightwood paleoseismology sites indicates that earthquakes on the southern San Andreas fault caused rockfalls 200 to 400 km to the north. A major rockfall event at about A.D. 1690 supports the Fumal et al. (1993) model for a San Andreas fault earthquake that was not detected at Pallett Creek. The A.D. 1690 event in the chronology indicates that the earthquake recurrence interval was shorter and that the degree of clustering of times of earthquakes was less on the Mojave segment of the San Andreas fault than previously thought.

Landslides and slope failures in Scotland: A review

Abstract Almost all documented landslides in Scotland belong to one of four categories: non‐rotational rock slope failures (major rockfalls, translational slides, topples or sags, often in some combination); rotational rock slope failures; debris flows; and translational slides in drift or regolith. Non‐rotational rock slope failures are particularly common on Highland metamorphic rocks, especially schists, and on igneous scarps in the Hebrides and Midland Valley; rotational rock slope failures almost invariably occur in weak sedimentary rocks overlain by resistant igneous rocks; and debris flows are most common on sandy drift or regolith. Former glacial activity has also been of importance in determining landslide distribution. The great majority of rock slope failures are ancient features, but debris flows and small translational slides in drift (both triggered mainly by intensive rainstorms) are much more frequent at present and cause much greater damage, particularly to communications.

A mathematical model for predicting the extent of a major rockfall

A mathematical model for predicting the extent of a major rockfall

The Pyrenees earthquake of 1660: Effects in France

Until 1975 or so, scientists' knowledge of the major earthquake of 1660 in the Pyrenees (in Bigorre) was largely restricted to the meagre information repeated in the classical catalogues. Useful material published in local learned journals was mostly unknown, and has only been unearthed and interpreted since 1976, when two year's work of analysis was started for the "Projet Sismo-tectonique" in France. During and since that project, further routine work necessary for the revision of the historical seismicity of France, has brought to light a new wealth of information from archive sources. This new knowledge, at least from the French side, is used as the basis for a brief macroseismic review of the event north of the Pyrenees, putting forward proposals for the isoseismal lines. Emphasis is placed on the number and quality of the sources, some of which are quoted for evidence of major rockfalls in the meizoseismal region and the wide extent of the felt area, as far north as Salnt-Maixent in Poitou.