Discontinuities within large rock slope failures are able to provide critical insights into the prevailing stress and strain regimes governing the behaviour of these unstable rock masses. To capture the true displacement vectors—essential for accurate failure mode characterisation and computation of the near-surface stress state—information about their kinematic behaviour must be obtained in three dimensions. Yet only a few extensometers have been designed for this purpose. This technical note presents an innovative contactless laser positioning system that employs a triangulation approach to generate three-dimensional records of fault and fracture behaviour in near real time. The positioning system comprises a sensing unit—a pair of laser modules, a digital camera, and a customised target—and a control unit together with a processing unit hosted on a remote server. Images of the target are acquired at regular intervals and transmitted to the server, where a semiautomated image processing protocol transforms the beam patterns into accurate three-dimensional measurements. Its accuracy is characterised by a maximal standard deviation in a single-axis measurement of 0.04 mm, and its precision is estimated to be better than 0.02 mm. Two of these devices have been tested on a large rock slope failure located on the eastern flanks of the Aiguilles Rouges in south-eastern France. Although the site posed a range of technical and logistical challenges, it is clear that the laser positioning system is capable of detecting complex kinematic fracture behaviour, opening the door for its integration into more comprehensive landslide monitoring programs.

The Outer Western Carpathians are fractured by several syn-thrust and post-thrust faults. One of them, the Mikulov Fault, has been studied using a combination of surface and subsurface methods. The former comprised the analysis of a LiDAR digital terrain model and aerial photographic interpretation while the latter comprised the analysis of ERT profiles and 2D seismic reflection profiles interpreted with the aid of borehole data. Paleostress analysis has also been used to understand the stress history and progressive development of the fault. By combining these methods it has been possible to define a distinct N-S directed fault zone that intersects or delineates the majority of the Jurassic limestone nappe outliers around the highlands of Pavlov Hills. This almost continuous fault zone runs for several kilometers on the Czech side of the border and extends further south into Austria. The thrusted Jurassic limestone bodies are cut by the fault zone, which tectonically crushed the limestone in its core and the cores of the secondary fault branches. The mapped pattern of the fault zone suggests branching and reattaching with the production of lenticular tectonic slices. Consequently, we interpret the fault as a prominent sinistral shear zone. This is indicated on the surface by block displacement on Svatý kopeček Hill and by the orientation of the accompanying subvertical Riedel shears with identified horizontal lineation. Subsurface kinematic indication derives from the interpretation of a prominent negative flower structure in the deep seismic profiles, just beneath the fault zone. The ERT profiles have revealed that the limestone bodies are tectonically bound by accompanying fault branches. Moreover, paleostress analysis suggest that fault zone activity can be divided into three main stages: (i) NE-SW thrust faults indicate thrusting of the Carpathian accretion wedge over the Bohemian Massif; (ii) NE-SW strike-slip faulting, during which the fault blocks moved along the faults in the direction of propagating wedge; (iii) N-S strike-slip faulting, marking the change in compression direction and transition from thrusting to a strike-slip regime. The main movement along the fault is probably of the late Miocene age and probably continues to the present day. The research was funded by the Grant Agency of the Czech Republic (GC22-24206J).

Accretionary wedges of orogenic belts develop differently based on the direction of thrusting, which can be perpendicular to oblique to the belt. In the case of oblique thrusting, stress partitioning occurs, which dissects the accretionary wedge, changes the tectonic regime from thrusting to strike-slip, and causes the external parts to rotate laterally. The relationship between stress partitioning and external rotation is not yet fully understood and has typically been studied separately. This study investigates the Falkenstein-Mikulov fault zone in the Outer Western Carpathians (OWC) wedge as an illustrative example of the relationship between partitioning and rotation. Using a prominent limestone marker horizon and a multidisciplinary approach—including geomorphological analysis, geological mapping, paleostress analysis, and shallow and deep-seismic geophysical surveys—we defined the fault zone’s unique arcuate geometry and identified several stages of tectonic activity. Paleostress inversion reveals multiple tectonic phases highlighting a transition from thrusting to strike-slip faulting. After thrusting (Phase D1), transversal strike-slip faults segmented the wedge coinciding with significant counterclockwise rotational patterns (Phase D2). Finally, during Phase D3, an arcuate strike-slip fault zone parallel to thrusting direction evolved, also revealing rotation of 12° over a distance of 10 km. These phases interplayed in the accretionary wedge at the same time, and their apparent succession is the result of shifting of the tectonic activity during the progressive development of the wedge. Thus, the thrusting activity in the front of the wedge was followed by rotational motion along the lateral ramps and finalized by parallel strike-slip faulting. This model explains how accretionary wedges undergo external rotation due to curved strike-slip faulting in the final stages of thrusting and has significant implications for understanding the broader tectonic evolution of accretionary wedges worldwide.

Eastern Part of the Czech Republic in the Outer Western Carpathians (OWC), particularly the Javorníky Mts. range along the Czech-Slovakian border, has been traditionally considered a geologically stable region with documented low contemporary seismic activity. However, recent geomorphological analyses and field investigations reveal compelling evidence of prehistoric large-scale and highly mobile mass movements, potentially triggered by paleo-earthquakes. This study integrates high-resolution LiDAR mapping, field investigations and trenching, geophysical surveys, radiometric dating, and numerical modeling to reconstruct the paleo-seismic characteristic of the region. We identified those paleo-landslide features using high-resolution LiDAR data and assumed their relationship to past seismic activity by their close vicinity to a Holocene polyphase surface rupture of the Lidečko Fault. LiDAR mapping combined with the Electrical Resistivity Tomography (ERT) analyses provide valuable insights into the structural geology, lithology, failure mechanisms of paleo-landslides. Trenching and dating techniques, including radiocarbon and optically stimulated luminescence (OSL), help establish the timing of these events and their possible seismic triggers. Structural analysis of the Lidečko revealed the active strike-slip and oblique reverse kinematics with surface ruptures and liquefaction features, supporting the hypothesis of the landslides´ earthquake-induced origin.Distinct three generations of landslides were identified as half-ellipsoidal depleted source zones about 400 m long, 200 wide and about 25 m deep with remnants of their accumulations at the toe and in the valley floor and different state of subsequent reworking by shallow slope processes. The fluidized mass was displaced for up to 1 km, of which up to 600 meters comprised totally flat riverbed. Radiometric dating of associated landslide-dam deposits revealed the landslides´ ages about 91 ka, 45 ka and 1.8 ka ago.To accurately assess their potential coseismic origin, synthetic seismic acceleration data derived from waveform records in the OWC region is integrated into both Newmark Displacement Analysis (NDA) with the Velocity-Dependent Friction Law (VDFL) and the distinct element numerical modeling. This combined approach improves the simulation of rock mass and landslide dynamics under seismic loading conditions and ensures a more precise analysis of earthquake-induced slope processes. Specifically, PFC3D numerical modeling is employed to reconstruct the paleo-topography and simulate the long run-out behavior of paleo-landslides under various earthquake scenarios. These simulations provide deeper insights into the triggering mechanisms and movement patterns of such landslides.The estimated magnitudes of past earthquakes challenge assumptions about the OWC's seismic stability and suggest significant unrecorded events. This study improves understanding of earthquake-induced landslides in stable regions and offers a framework for assessing long-term seismic hazards. The methods used can be applied to other areas with uncertain seismic histories, helping to better understand the connection between tectonics and landscape evolution.The research was funded by the Grant Agency of the Czech Republic (GC22-24206J) and Taiwanese National Technological and Science Council (MOST/NTSC 111-2923-M-008-006-MY3).

The Outer Western Carpathians, situated in the central European segment of the Alpine-Himalayan orogenic zone, present an intriguing case of an accretionary wedge. This region is characterized by Mesozoic and Cenozoic flysch sedimentary rocks, comprising massive sandstone benches and intercalated clay layers. These formations have undergone significant deformation, including being thrust over the European foreland during the Paleogene and Neogene periods. The resulting hilly to mountainous terrain exhibits notable slope failures. Here we focused on the phenomenon of under-dip toppling –sandstone beds steeply dipping in the direction of the slope, which were locally overturned along systems of brittle fractures. Utilizing high-resolution LiDAR data, our study investigates the locations, geometrical characteristics, and tectonic settings of these toppling. In the Javorníky Mountains, these topples predominantly occur in SSE-dipping fold limbs, an orientation conducive to under-dip toppling. The mechanism of under-dip toppling, involving the lifting of the center of gravity of the toppled layers, presents a complex geomechanical challenge. Recent field investigations, including structural measurements on faults, electrical resistivity tomography (ERT) profiles, and 10Be dating, have identified active polyphase strike-slip surface ruptures in the region. These findings raise questions about the origins of toppling and their implications for understanding paleo-earthquakes in the area. Our preliminary analysis suggests a two-tiered approach to understanding toppling processes: firstly, exploring the deeper structural implications – could active tectonic faulting be the cause of the under-dip toppling? Secondly, we analyzed the mechanism of toppling near to the surface. By analyzing the geometry of near-surface persistent sandstone slabs and employing Pseudo-static analysis to assess seismic slope response, our results indicate that the layer while overturned may be attributed to strong paleo-seismic events. This study employs comprehensive site investigations and back analyses to understand a range of possible trigger and controlling mechanisms. It elucidates the geological conditions of slopes and performs a geomechanical analysis of under-dip toppling. The research is part of the international bi-lateral project “Earthquake triggered landslides in recently active and stabilized accretionary wedges”, supported by the Czech Science Foundation (GAČR 22-24206J) and the Taiwanese Ministry of Science and Technology (NTSC 111-2923-M-008-006-MY3).

Short-term earthquake prediction remains one of the primary goals of seismotectonics. Here detailed observations of unusual fault kinematic behaviour and near-surface crustal stress variations are presented from before, during, and shortly after an earthquake series which culminated with two Mw 4.6 and 4.4 events near Breitenau, Vienna Basin, Austria, on 30 March 2021 and 19 April 2021, respectively. The oblique normal NNE-SSW trending Pitten Fault is exposed in Altaquelle Cave close to the southern margin of the Vienna Basin in the eastern Alps, which is known to have hosted several historical earthquakes of Mw = > 5. This cave has developed in Triassic marbles of the Central Alpine Permomesozoic. The observed branch of this active steeply dipping fault is associated with the seismogenic sinistral Vienna Basin Fault and the NE-SW trending Mur-Mürz Fault. To investigate the fault activity, TM71 moiré extensometers have been used to obtain precise three-dimensional records of fault kinematic behaviour at the micron scale while the recently developed SMB2018 protocol has been used to define the stress state associated with each fault reactivation event. The observations were then compared to the Copernicus European Ground Motion Service InSAR time series derived from Sentinel-1 data. From late 2018 to early 2021, the three-dimensional kinematic behaviour of the fault comprised a variety of different on-plane as well as out-of-plane hanging block displacements ranging in magnitude from 3 to 19 μm. Then, around the time of the earthquake series in 2021, four significant displacement events were recorded: (i) 0.186 mm along a vector of 186/-12° (i.e. upward) on 16 March; (ii) 0.615 mm along a vector of 177/-88° (upward) on 26 March; (iii) 0.066 mm along a vector of 013/26° (downward) on 30 March; and (iv) 0.022 mm along a vector of 308/54° (downward) on 11 May. The third of these events occurred on the same day as the largest earthquake. These events are all much larger than any other record of fault displacement recorded in the Eastern Alps since 2013. This contribution details this unusual fault displacement behaviour and compares the calculated stress states with both the focal solutions for each earthquake and InSAR maps of E-W and vertical ground motion. A comprehensive understanding of this important seismotectonic event helps to shed further light on potential earthquake precursory phenomena.

Stress variations in the Earth's crust need to be understood in both the spatial and temporal domains to address a number of pressing societal issues. In this paper, precise three-dimensional records of fault kinematic behaviour obtained by mechanical extensometers are used to investigate changes in stress states along major faults in the Eastern Alps. The monitored faults are fractures with evident Upper Quaternary displacement and are directly attributed to their master tectonic structures. The results demonstrate that activity at the submillimetric scale is highly episodic; periods of repose are punctuated by conspicuous reactivation events affecting one or more of the displacement components. An original approach named the SMB2018 method is used to define the stress state associated with each fault reactivation event. The outputs evidence significant short-term changes in the local stress regime. The directions of the principal normal stresses calculated from these reactivation events present generally similar patterns for both compressional and extensional stress states. Consequently, submillimetric fault activity cannot be controlled by a rotating stress field; such shifts can only be caused by a change in the magnitude of the individual principal normal stresses so that the maximum compression changes to the minimum and vice versa.

AbstractThis paper describes a comprehensive online database of giant landslides on volcanic islands compiled by researchers from the Institute of Rock Structure and Mechanics, Czech Academy of Sciences, in the framework of IPL Project 212. The database was constructed from 2016 to 2018. It comprises a total of seventy-five events from the Atlantic Ocean and Mediterranean Sea, sixty-seven events from the Pacific Ocean, and forty events from the Indian Ocean. In this paper some of the main benefits of landslide inventories and thematic databases are outlined and the global distribution of giant landslides on volcanic islands is described in depth. The database is hosted on the website of the Institute of Rock Structure & Mechanics and records can be downloaded as a spreadsheet or kml file for integration in a number of geospatial programs including ArcGIS and Google Earth. However, since completion of the database in 2018, a number of potentially significant studies of giant landslides on volcanic islands have been published from archipelagos in the Atlantic and Pacific Oceans while outstanding modern analogues for past events are represented by the collapse of Anak Krakatau on 22 December 2018 and the collapse of Hunga Tonga-Hunga Haʻapai on 15 January 2022. Consequently, the recent literature will be scrutinized with the aim of updating information already contained in the database while two new layers are planned: the first of these will provide information about recent volcanic collapses and the second will provide information about the long-term instrumental monitoring of giant landslides. It is intended that the second release of the database will be available online in early 2023.

Precise 3D dilatometric monitoring began on the San Andrés megalandslide detachment plane on El Hierro, Canary Islands, during the winter of 2013. It has been found that this presumably aborted giant landslide creeps progressively at rates of up to 0.5 mm a−1, with accelerations following periods of seismicity and extreme rainfall. In addition, a detailed multidisciplinary investigation of the landslide detachment plane has found that silica and cataclastic layers were produced during a pair of discrete slip events at 545–430 ka and 183–52 ka. Furthermore, slope stability analysis has suggested that creep may result from the deformation of sedimentary layers in the ocean, while destabilisation of the volcanic flank would require an earthquake with an intensity of at least VII. Finally, simple tsunami modelling based on conservative scenarios has shown that even a comparatively small event could have severe ramifications along the coasts of northwest Africa and southwest Europe.

Ultralow frequency (ULF) to low frequency (LF) electromagnetic radiation represents one of the most promising effects of brittle rock strain and microcracking that might be potentially helpful for short term earthquake forecasting. In this study the results of a six month monitoring campaign are presented from Obir Cave in the eastern Alps. Direct experimental observations of electromagnetic radiation have been made using a customised broadband data logger installed next to the Obir Fault - this seismogenic fault near the Periadriatic Lineament is known to be related to at least three large prehistoric earthquakes. On the basis of these measurements it has been possible to characterise a number of distinct signals: artificial constant narrowband signals at discrete frequencies; short serial broadband impulses; high energy broadband impulses; and low energy broadband impulses. The narrowband artificial signals were removed from the electromagnetic radiation time series analysis so that the natural signals were enhanced and could be compared more easily to meteorological parameters and rock strain indicators. Critically, the high energy broadband impulses show a strong correlation with lightning activity across much of central Europe and the eastern Mediterranean while the low energy broadband impulses appear to be associated with local rock strain in and around Obir Cave. Unfortunately, it seems certain that some of the essential strain related impulses are likely to have been overprinted by the larger lightning related impulses.

Spectacular geomorphic evidence of recent tectonic activity and three potentially strong prehistoric earthquakes were discovered in Obir Caves in the Karawanken Mountains. This paper presents active fault structures, geomorphic features, and the age constraints attributed to particular seismotectonic events. The 1976 Mw 6.7 Friuli earthquake about 100 km from Obir Caves caused only local speleothem damage. The 100 km hypocentral distance enabled attenuation of the seismic waves so speleothem damage due to stalagmite resonance frequency was dampened. The documented dripstone column damage was rather caused by its sudden shortening due to passing elastic S-waves with estimated 3.5 (+8.2/-1.5) mm PGD amplitudes. At least three distinct seismotectonic events in the Late Pleistocene and Early to Middle Holocene were constrained by radiometric dating. The 40.6 cm sinistral fault slip occurred between 41.8 +/- 1.3 ka and 18.7 +/- 0.4 ka ago, the 2.6 cm dextral oblique reverse fault slip happened between 10.73 +/- 0.23 and 8.61 +/- 0.15 ka ago, and another speleothem damage event took place between 6.28 +/- 0.24 ka and 5.7 +/- 1.2 ka ago. These events were most probably accompanied by distinct destructive to very destructive paleoearthquakes with local intensities ranging from VIII to X on the ESI 2007 scale, significant rock weakening, and forming the large deep-seated gravitational slope deformation on the southeastern mountain slopes adjacent to Obir Caves.

Volcanic flank collapses often result in giant debris avalanches that are capable of travelling tens of kilometres across the ocean floor and generating tsunamis that devastate distant communities. The San Andres Landslide on El Hierro, Canary Islands, represents one of the few places in the world where it is possible to investigate the landslide mass and fault planes of a volcanic collapse structure. In this study, a new conceptual model for the development of this enormous slump is presented on the basis of structural geological and geomorphological measurements, petrological and microstructural analyses, and cosmogenic radionuclide dating. Structural geological and geomorphological measurements indicate that the fault plane records two distinct events. Petrological and microstructural analyses demonstrate that a thin layer of frictionite covers the surface of the fault in contact with an oxidised tectonic breccia that transitions into the underlying undeformed basanite host rock. This frictionite comprises a heterogeneous cataclastic layer and a translucent silica layer that are interpreted to represent two separate slip events on the basis of their architecture and crosscutting relationships. Cosmogenic He-3 dating reveals a maximum exposure age of 183 +/- 17 ka to 52 +/- 17 ka. Arguments are presented in support of the idea that the first slip event took place between 545 ka and 430 ka, prior to significant clockwise rotation of El Hierro, and the second slip event took place between 183 ka and 52 ka, perhaps in association with one of the giant debris avalanches that occurred around that time. This is the first time that more than one slip event has been recognised from the fault plane of the San Andres Landslide. It is also believed to be the first time a silica layer resulting from frictional melt has been described in a volcanic setting.

The first comprehensive global database of giant landslides on volcanic islands is outlined in this report. This database comprises a total of one hundred and eighty-two entries: the Atlantic Ocean hosts seventy-five giant landslides; the Pacific Ocean hosts sixty-seven giant landslides; and the Indian Ocean hosts forty giant landslides. To determine the spatial characteristics of each giant landslide, it has been necessary to georeference published maps using ArcGIS software coupled with global DTMs. Using the georeferenced outputs, it has been possible to measure the basic morphometric characteristics of each landslide such as its length, width, perimeter, area, and fall height. Landslide volumes have been calculated with a higher degree of certainty in thirty-five cases and with a lower degree of certainty in sixty-three cases while complete outlines of the landslide area have been defined in ninety-six cases. On the basis of these data, it has been possible to interrogate relationships between potentially significant variables. The age distribution of giant landslides on volcanic islands demonstrates that more than half of the records in the database occurred during the last 0.5 Ma. This global database of giant landslides on volcanic islands is hosted on the website of the Institute of Rock Structure & Mechanics: https://www.irsm.cas.cz/ext/giantlandslides . From there, the records can be downloaded as a spreadsheet or as a kml file for interrogation in a number of geospatial software programs including ArcGIS and Google Earth. This work is part of the activities of the International Consortium on landslides, namely, its International Programme on Landslides (Project No. 212).

Giant landslides on volcanic islands represent the largest formations which can be created in a single geological moment. Such landslides are distributed across the globe and have attracted a significant amount of research interest. Yet, no coherent attempts have been made to rationalise this information into a single online resource. This report summarises information about the structure of the recently created database of giant landslides on volcanic islands and presents some observations regarding the uncertainties inherent in the inventories. The database is being prepared over a 3-year period: the first year of the project has focused on rationalising information about giant landslides around the Atlantic Ocean while the second and third years will focus on rationalising information about such landslides from the Pacific Ocean and Indian Ocean, respectively. Using this database, it should be possible to interrogate the spatial and temporal patterns of land sliding and landslide reactivation as well as to better assess the hazard and potential risks posed by giant landslides on volcanic islands. It will be particularly interesting to see if any evidence can be found for global triggers, such as eustatic or climatic changes, instead of the more commonly expounded local triggers. Ultimately, it is hoped that the database will benefit both the geoscientific community and those agencies responsible for civil defence. This work is part of the activities of the International Consortium on Landslides, namely its International Programme on Landslides (Project n. 212). The database is available from the giant landslides project webpage: https://www.irsm.cas.cz/ext/giantlandslides .

Karst landforms can result from a single stage process in which chemical dissolution and mechanical erosion proceed simultaneously or from a two stage process in which chemical dissolution precedes mechanical erosion. During the second of these processes, chemical dissolution leads to the creation of karst features hosting a residual weathering product, here referred to as alterite. An example of one such feature is the enclosed mass of altered rock at Cerveny Quarry near Klukovice which represents one of the richest localities for exceptionally preserved echinoderm ossicles in the Prague Synform. In this study the processes responsible for the formation of this feature have been investigated. Nineteen samples were obtained from the bioclastic Slivenec Limestone and from these it has been possible to calculate the carbonate volume content, which defines the weathering intensity, and the carbonate rock weathering index, which defines the weathering state. The results demonstrate that carbonate dissolution has not been accompanied by gravitational compaction or the incorporation of mineral inputs. Thin sections analysed under polarised light and under cathodoluminescence emphasise heterogeneous dolomitisation of the limestone. As the weathering grade intensifies, empty rhomboidal pores become increasingly common until, ultimately, the rhomboidal forms are lost due to corrosion and enlargement. In contrast it is rare to find evidence of calcite dissolution and, therefore, the altered mass still hosts almost all of its post dolomitisation micrite, sparite, and bioclasts. Negligible calcite dissolution helps to explain the exceptional nature of the fossil preservation at the site while the dolomite dissolution accounts for the ease with which it is possible to extract the fossils. Further research should focus on better understanding the role of dolomite dissolution in the formation of other important palaeontological localities in the Prague Synform.

Composed volcanic edifices are particularly prone to large-scale failures—these often result from the acceleration of preexisting deep-seated gravitational slope deformations. Consequently, a complete understanding of the kinematic behaviour of such slope deformations would represent an important step towards mitigating against human casualties or fatalities and damage to critical infrastructure. In this manuscript, a 9-month time series of three-dimensional fault displacement measurements has been used to determine the stress states of the San Andrés Landslide on El Hierro in the Canary Islands. These stress states have been calculated on the basis of single-displacement events using a novel approach which only requires information about the magnitude of the movement vector and its orientation. The analysis focused on four specific periods: a reference period in November 2013; an extreme rainfall event at the beginning of December 2013; and two endogenous impulses at the end of December 2013 and during the middle of March 2014. On the basis that the direction of principal stress represents a marker for the direction of landslide mass movement, it has been possible to define six landslide activity modes which correspond to specific stress states. The response of the landslide to the extreme rainfall event was immediate and reflected increasing saturation of the porous landslide mass. The response of the landslide to the endogenous impulses was more complicated as compressional pulses often alternated with gravitational relaxation. In this study, it is demonstrated that the landslide stress state can be determined on the basis of a single-displacement event whenever fault displacements are monitored in three dimensions. This innovative approach may represent a valuable step towards a complete understanding of the kinematic behaviour of potentially catastrophic slope deformations, particularly those which are in a critical stability state.

In this paper, a contactless positioning system is presented which has been designed to monitor the kinematic behavior of mechanical discontinuities in three dimensions. The positioning system comprises a neodymium magnet, fixed on one side of a discontinuity, and a magnetoresistive sensing array, fixed on the opposing side. Each of the anisotropic magnetoresistive sensors in the sensing array records the magnetic field along three orthogonal directions. The positioning system intrinsically generates compact data packages which are transmitted effectively using a range of standard wireless telecommunication technologies. These data are then modeled using a global least squares fitting procedure in which the adjustable parameters are represented by the position and orientation of the neodymium magnet. The instrumental resolution of the positioning system can be tuned depending on the strength of the magnetic field generated by the neodymium magnet and the distance between the neodymium magnet and the magnetoresistive sensing array. For a typical installation, the displacement resolution is shown to be circa 10 μm while the rotation resolution is circa 0.1°. The first permanently deployed positioning system was established in June 2016 to monitor the behavior of an N-S trending fault located at the contact between the eastern Alps and the Vienna Basin. The robust design of the positioning system is demonstrated by the fact that no interruptions in the broadcasted data streams have occurred since its installation. It has a range of potential applications in many areas of basic and applied research including geology, geotechnical engineering, and structural health monitoring.

A small mesh of sensors which monitor movements across detachment planes of the giant San Andrés Landslide on the northeastern lobe of El Hierro in the Canary Islands was established in 2013. In this paper we present the results obtained over a two year period spanning from October 2013 to October 2015. Our results demonstrate that the detachment planes are affected by sinistral strike slip displacements and subsidence of the depleted mass of the landslide. While these general trends are consistent the movements recorded at particular monitoring points differ in detail as one site is characterised by progressive strike slip and dip slip trends while another is characterised by movement pulses and reversals in the sense of movement. These findings contrast markedly with suggestions that the giant landslide is inactive and demonstrate that its reactivation is a possibility which cannot be dismissed categorically. Big data analytics have been used to identify interdependence between the recorded movements and a range of climatic and geophysical variables such as seismic data, tidal data, and geomagnetic data. We have found that the recorded movements correlate only weakly or moderately with climatic and seismic parameters but strongly to the horizontal and vertical intensity of the magnetic field. These findings are rather unexpected and we emphasise that special care must be taken in pushing the conclusions of a purely numerical analysis. The advantages of adopting a big data mindset led us to make significant improvements to the instrumental infrastructure in early 2016. These incremental improvements to the small mesh of sensors are driven partly by our desire to understand the kinematic behaviour of landslide itself and partly by our desire to explore the potential of big data analytics in geoscientific research.