We present the results of 3-D monitoring of strain along active faults outcropping in the central Apennines, where recent and historical strong earthquakes occurred, using TM-71 extensometers during the period 2002–2017. We discuss the fault slip development as well as kinematics particularly in the light of local recent seismicity. The recorded fault slip corresponds to the minimum and maximum principal stress with a SW-NE orientation and slightly dipping to SW. Moreover, the detected fault slip is non-linear and affected by remarkable transient periods of acceleration, which lasted up to several months. The recorded accelerations were induced by alternation of extensional, reverse and horizontal displacement due to switching extensional and compressional stress/strain state and coincide with periods of major seismic events that recently affected the central Apennines. This phenomenon is being investigated. In the case of the moderate L'Aquila 2009 and Norcia 2016 earthquakes, the recorded fault slips can be characterized as pre-seismic.

Rock block forms of the Szczeliniec Wielki (919 m a.s.l.) in the border area of the Stolowe Mountains massif originated due to various exogenous and endogenous processes. The processes had started in the Upper Cretaceous, culminated in Late Tertiary, and continue till the present day with much lower intensity. Such processes were indicated by historical earthquakes and different tectonic events in the Sudeten Mountains and adjacent areas. Results of geodetic geodynamic studies are presented. Several sectors of the Sudeten Mountains which include the Table Hills - Stolowe Mountains, show horizontal and vertical movements. Results of periodic precise levelling in three geodetic micro-networks established on the Szczeliniec Wielki: "Przy Schronisku", "Piekielko" and "Tarasy Poludniowe / Schody" are presented. Investigations have been augmented with TM-71 crack gauging in rock blocks. These studies started in 1972 increasing gradually effectiveness of monitoring. Levelling changes, as well as displacements resulting from 3D monthly records of three TM-71 crack gauges have been confronted with recent investigations into tectonic micro-deformations along the Sudeten Fault in the Bohemian Massif. It is suggested that aseismic geotectonic processes participated in the deformations found in investigated networks.

In this paper, results from the long-term monitoring of two deep-seated slope deformations are presented. These deformations are considered typical of the types of landslide that occur in the high mountains of the Western Carpathians. The localities are situated in similar geological settings and this has enabled direct comparison of their development over the past 30 years. The monitoring has been undertaken using the extensometric gauges, TM71. At the Parohy Site, results from the scarp area show a significant vertical displacement trend of 0.07 mm per year. At the Strochy Site, results from the crown area show a horizontal crack opening trend of 0.015 mm per year. Monitoring is ongoing at both sites.

Long-term geotechnical monitoring of crack and fissure movements in slope deformations, historical buildings, as well as underground objects in Slovakia, provided results that bear evidence of movement trends, as well as of present tectonic unrest. The results were subject to an analysis regarding anomalies in movements that would verify activity of a specific geodynamic process. Such a process was detected recently in the Bohemian Massif and evidenced even in other European countries, north as well as south of the Alps. The process began by a tectonic pressure pulse and followed by a phase of increased geotectonic activity. The search for signs identifying this process on the Slovak territory which belongs to a different geological unit than the Bohemian Massif was successful. This is further evidence that the process in question is of a very deep foundation. The investigations proved successful long-term outdoor operation of TM71 crack gauges working on the principal of mechanical interference between optical grids. A thirty year long record was even reached. A useful function of the gauge which allows for supplementary data about angular deviations in faults has been found useful in the analysis. The data indicate affinity of the process to a large global disturbance in the Earth crust.

It is possible to monitor slow-moving landslides and assess landslide stabilisation measures over protracted periods using an optical–mechanical crack gauge called a TM-71. This technical note outlines the theoretical background to the gauge and illustrates its practical application through a number of case studies. These studies are drawn from a range of landslide types and stabilisation measures. In terms of monitoring slow-moving landslides, three studies of deep-seated deformations are presented. The Taukliman coastal landslide on the Black Sea Coast is characterised by vertical and horizontal displacements of up to 0.2 mm year−1 and sudden earthquake-induced dilations of up to 6 mm. The Parohy ridge spreading landslide in the Malá Fatra Mountains is characterised by gravitationally induced vertical displacements of 0.7 mm year−1. The slope deformation that formed Cyrilka Cave in the Beskydy Mountains is characterised by very slow sinistral strike–slip movements of 0.8 mm year−1. In terms of assessing landslide stabilisation measures, two studies are presented from Orava Castle in Slovakia and Tetín in the Czech Republic. The data recorded at these sites demonstrate that the constructed stabilisation measures have successfully alleviated the potential landslide hazard in both localities. These case studies clearly demonstrate that the gauge represents an important tool with which to monitor slow-moving landslides and assess landslide stabilisation measures. It is able to provide a precise three-dimensional record of deformation, withstand harsh environmental conditions, and record reliable data over protracted periods.

At the end of 2010 seven TM 71 extensometers, installed at or near the active faults in Slovenia, were in operation. Three of them are on the surface and four inside karst caves. The highest rates with stable sense of movements were observed on the Idrija fault. Average horizontal displacement rate was 0.24 mm/year. Short term rates were even greater and reached 0.54 mm/year. The Rasa fault first experienced an uplift of the SW block of 0.16 mm/year, which was followed by a short-term down-slip of the same block at the rate of 0.37 mm/year. Later the sense of movement returned to uplift with a rate of 0.05 mm/year. The average horizontal displacement was 0.07 mm/year. The Kneza fault experienced very small average displacements (y=0.035 mm/year, z=0.03 mm/year and x=0.02 mm/year). Similar rates were observed in nearby Polog cave (y=0.015 mm/year, z=0.027 mm/year and x=0.016 mm/year), which is located close to the seismically active Rayne fault. For Kostanjevica cave, located near the Brezice fault, small average rates are characteristic (y=0.006 mm/year, z=0.017 mm/year and x=0.012 mm/year). In Postojna cave, located close to the Predjama fault, two monitoring sites are very stable with small tectonic movements, including general dextral horizontal movement of 0.05 mm from 2004 to 2010 (Postojna 1) and two significant short-term peaks of 0.08 mm (Postojna 1-y and Postojna 2-z).

This paper examines the results of fault microdisplacement analyses obtained from sites located both at the surface and underground in western Slovakia. The results of surface monitoring showed significant annual climatic effects on the various displacement components. In contrast, the results of underground monitoring in caves showed minimal climatic effects. It is seen that the influence of climate decreases markedly with depth. The yearly peak-to-peak amplitude of climatic variations may be as high as 1 mm at the surface but only 0.1 mm underground.The amount of tectonic displacement can be determined once such climatic considerations have been taken into account. Our fault displacement measurements show horizontal strike-slip rates of tenths of mm or hundredths of mm per year. In addition, vertical displacements have been recorded at Prekazka Quarry, Driny Cave, and Slopy Cave. The network is sufficiently dense to identify changes in displacement activity recorded during recent, significant, earthquake events. Furthermore, three gauges have also helped to determine the local stress orientation in Driny Cave.

This paper presents the results of a long-term monitoring study undertaken during the period 2002–2007. The study recorded the displacement of various widely-distributed tectonic structures along the generally aseismic Bohemian Massif (Czech Republic) and specifically along the Sudeten Marginal Fault Zone. The derived results were compared with data recorded over the same time period in the Upper Rhine Graben (Germany), Central Apennines (Italy), and the Gulf of Corinth (Greece). It is clear that a tectonic pressure pulse initiated a period of increased geodynamic activity across central and southern Europe during the course of our monitoring. Within the Bohemian Massif, the pressure pulse was first recorded in mid 2003 and the ensuing period of increased geodynamic activity lasted for nearly three years. This period is associated with compression along the Sudeten Marginal Fault Zone. The southern flank was repeatedly downthrust beneath the northern flank, which caused the latter to continually uplift and subside. The period of increased geodynamic activity was terminated by two strong local earthquakes. Consequently, it is considered that this period induced earthquake activity within the Bohemian Massif. When taken together, the presented data provides robust evidence for the reconfiguration of stress and strain relationships within central and southern Europe. Whilst it is possible that tectonic activity in the Alps produced a north-verging pressure pulse that affected central Europe (e.g. in the Bohemian Massif and Upper Rhine Graben), it cannot account for the pressure pulse recognised to the south (e.g. in the Central Apennines and the Gulf of Corinth). Due to the predominance of vertical movements, it is suggested that this reconfiguration results from deep seated processes within the lithosphere–asthenosphere. However, the influence of horizontal movements transmitted from the compressional zone between Africa and Europe cannot be discounted.

This paper provides evidence for recent geodynamic activity within the Sudeten and Krusne Hory Mts. Fault Zones of the Bohemian Massif, Central Europe. Data were recorded using crack gauges and tilt-meters located on specific geological structures within caves and galleries. These data are supported by rangefinder, seismic, and groundwater observations. It is shown that a significant pressure phenomenon, here termed a pressure pulse, occurred during 2003. The pressure pulse initiated a series of tectonic deformations. In the Krusne Hory Mts., the pulse was preceded by chaotic tilt movements followed by significant tilt reorientation. Several stages of the deformation process were determined, analysed, and described. These stages represent stability, relaxation, compression, compaction, and later relaxation. The pressure pulse itself was associated with the compressional stage. Moderate, but regionally significant, earthquakes occurred during the later stages of the deformation process. This precludes the idea that they might be responsible for the initiating the recognised movements. At the same time, an unusual sequence of earthquake micro-swarms occurred in West Bohemia. These events should all be seen as the result of tectonic deformation initiated by the pressure pulse. Supplementary data indicate an affinity between the deformation process and large global disturbance within the Earth's crust (Stemberk et al., 2010). (C) 2010 Elsevier Ltd. All rights reserved.

Micro-tectonic deformations have been monitored continuously in 3D in Postojna Cave, Slovenia with TM 71 extensometers since 2004. Two instruments, 260 in apart, were installed on the Dinaric oriented (NW-SE) fault zone that is situated about 1,000 m north of the inner zone of the regionally important Predjama Fault. Monitoring on both instruments has shown small tectonic movements (i.e., a general dextral horizontal movement of 0.05 mm in four years [Postojna 1] and extension of 0.03 mm in four years [Postojna 2]). Between the longer or shorter calm periods, eleven extremes have been recorded regarding characteristic changes in displacement. The largest short-term movement was a compression of 0.04 mm in seven days, detected in March 2005, which coincided with the 25 km distant Ilirska Bistrica earthquake (M-L = 3.9). About two months before the earthquake an extension of 0.05 mm occurred and one month before the earthquake the strain changed into a compression of 0.05 mm. The largest permanent peak was detected at the end of 2004. Along the y-axis (Postojna 1) there was a dextral horizontal movement of 0.075 mm in one month (November 10 to December 15, 2004). After the sinistral horizontal movement of 0.02 mm (December 15-27, 2004), the y-axis retained its permanent position on 0.05 mm, where it remained for more than a year. Regarding the extremes, ten earthquakes were selected that coincided with tectonic micro-displacements. In terms of speleogenesis, the monitored fault zone represents a stable cave environment. Because radon flux is known to change significantly during tectonic and seismic activities, radon air concentrations were monitored in parallel since 2006. During horizontal movements, either dextral or sinistral, radon pathways underground were partly closed, thus hindering radon migration and reducing its concentration in the cave air. Extension movements do not appear to have affected radon transport. Alternatively, the compression process (Postojna 2, February August 2007) appears to have opened some new routes for radon transport, facilitating radon migration and increasing its concentration in air.

The tectonic setting of W Slovenia is characterised by NW-SE trending dextral strike-slip fault systems and moderate seismicity. Monitoring of tectonic movements along five presumably active faults or in their vicinity using TM 71 extensometers was set up in 2004. In five years of monitoring some clear trends of displacement were established. The morphologically most prominent fault in W Slovenia is Idrija Fault having a total length of more than 120 km. The average lateral displacement measured along a crack in its inner fault zone in Učja valley was 0.26 mm/year. Short-term rates were even greater and reached 0.54 mm/year. Raša Fault monitoring site at the foot of Vremščica Mt. established first an average uplift of SW block for 0.16 mm/year and left-lateral displacement of 0.16 mm/ year. It was followed by down-slip of the same block at the rate of 0.37 mm/year. In Postojnska Jama two instruments, 260 m apart, were installed at the fault zone, which extends about 1 km northeast from Predjama Fault. We detect small tectonic deformations, dextral horizontal movement of 0.05 mm in 5 years for Postojna 1 and extension of 0.03 mm in 5 years for Postojna 2. Both devices recorded similar reactions to some earthquakes with magnitude range 3.1-5.2 and epicentral distance of 12-95 km. The amplitude of individual peaks is in the order of 0.08 mm. The monitoring at Kneža Fault started at the end of 2006. In two years clear oblique displacement was established with left-lateral rate of 0.06 mm/year and uplift of SW block for 0.06 mm/year. Monitoring in Pološka Jama situated in vicinity of the Ravne Fault started in 2008. Preliminary results show 0.08 mm of horizontal displacement between two limestone beds. Established displacements proved the active tectonic movement of all monitored faults. Observed deformation rates can be compared with the regional deformation rate in W Slovenia established from GPS measurement, which is in the order of 2 mm/year.

The results obtained by four years long TM 71 extensometcr monitoring of 3D micro-tectonic displacements of Dinaric Fault Zone on two sites, being 260 in apart in Postojna Cave, were statistically evaluated with different methods (Kolmogorov-Smimov test, comparison between relative displacement and earthquakes, linear regression, Kruskal-Wallis one-way analysis of variance, histograms and correlation coefficients). Responses to stress changes regarding x, y and z-axes are not the same on two monitoring sites even if we are monitoring the same fault zone. Kolmogorov-Smimov test for comparing the two curves is applicable only for three axes combination (Postojna 1 z - Postojna 2 z, Postojna 2 y - Postojna I z, and Postojna 2 z - Postojna 2 y). Kruskal-Wallis analysis is most representative for z-axes. Some sharp peaks coincide with earthquake occurrences (Krn M=5.2, Cerkno M=4.0, Ilirska Bistrica M=3.9, Brezice M=2.9 and Krsko M=3.1). Generally we detect very small tectonic deformations, dextral horizontal movement of 0.05 mm in 4 years for Postojna I and extension of 0.03 mm in 4 years for Postojna 2. Discrepancies between two sites can be attributed to complex geological structure and by the fact that studied fault zone is cut by cross-Dinaric fault zone.

Three year monitoring of micro-displacements on four tectonic fracture planes in a tunnel driven by a milling cutter into granitoids of Bohemian Massif revealed micro-movements that develop in certain trends and impulses. Two investigated fractures are of the Krusne Hory Mts. orientation (NE - SW), other two of Sudeten orientation (NW - SE). These have been found the two prevailing fracture orientations in the massif. Results from all the four fractures indicate trends in overfaulting of southern blocks over the northern ones and a stress state model characteristic of approximate N-S compression with overthrust vergence to N. Besides, some impulses were indicated with abrupt occurrence that dominates the development of movements. The first most significant impulse occurred by the end of the year 2004, the second one at the break of 2005/6. The coincidence of the impulses with earthquake events is discussed.

Bear Cave under Mt ¦nie¿nik is located near the Lower Sile­sian Village of Kletno in a wider tectonic fault zone of Sudeten, Klodzko Valley, South Poland. Stability requirements along the visitor’s path in the cave called for permanent checks of pos­sible rock movements in the massif, while mining operations in the neighbouring marble quarry represented major threat to cave stability. Precise levelling network for vertical movements in the cave and its vicinity was established about 20 years ago. Outside the cave in the Kle¶nica River valley levelling traverses were crossing tectonic faults. Periodical measurements have been repeated since 1984. In the cave two fault zones of major risk have been checked also with TM-71 crack gauges and re­cords have been taken with a month frequency. These two were the tectonic crack zones of the Water Corridor and the main fault structure of the cave found in the Cascade Alley. Fourteen years ago after finding that quarry blasts induced increased movements in the cave, quarry operations were stopped. Re­cently, gradual subsidence of some levelling bench-marks was observed, as well as some periods of increased micro-displace­ments on the tectonic crack zones. Such observations are dis­cussed.

This paper presents results of morphotectonic research carried out in order to determine the neotectonic development of the drainage network in the NE spur of the Bohemian Massif (central Europe). The area studied comprises the north-eastern sector of the Rychlebske Mts, belonging to the Sudeten Mountains and the adjacent part of the Zulovska Hilly Land in the Sudetic Foreland (Czech Republic). Analysis of drainage network characteristics such as cross-sections, erosion rate, longitudinal river profiles, stream length-gradient index (SL) and investigation of alluvial fans/terraces was performed using detailed geomorphological mapping and field examination, and DEM data. Moreover, a reconstructed neotectonic evolution was compared with present-day fault movements obtained by fault monitoring using the TM71 deformeter. The deformeter was installed directly across faults in two karst caves in the study area within the NW-SE striking Sudetic Marginal Fault (SMF) zone. This zone is one of the morphologically most prominent neotectonic structures in central Europe, separating the Sudeten Mountains from the Sudetic Foreland. Morphotectonic research reveals that segments of enhanced erosion correspond well with increased SL indices, changes in valley cross-sections and anomalies in the longitudinal profiles. The beginnings of the stretches of increased headward erosion/rejuvenated erosional phase are concentrated at the foot of marginal slopes of the mountainous sector of the study area, which supports the hypothesis that uplift of the mountainous sector is still expressed in its relief. Alluvial fans/terraces of three levels recognized in the adjacent Zulovska Hilly Land are of Middle to Late Pleistocene age: Saalian 1 (240-280 ka), Saalian 2 (130-180 ka) and Weichselian (10-80 ka), respectively. They postdate the retreat of the last continental ice-sheet, which reached the study area in Elsterian 2 (400-460 ka). Their relative heights above the river channel are greater than terrace levels of the same age along the main Nysa Klodzka River. The height differences attain 20 m at the highest level 1, at least 8 m at level 2, and up to 2-3 m at level 3. These discrepancies imply post-Saalian 1 uplift of the Zulovska Hilly Land relative to the topographically lower Nysa Klodzka valley.Monitoring of present-day tectonic movements in the studied area revealed slow micro-displacements (hundredths to tenths of millimetres per year). The displacements have an aseismic character and the vertical component always prevails over the horizontal one. The inferred compressive stress comes generally from the southern sector, which would imply dextral transpression in the studied portion of the SMF, where the northern part is thrusting over the southern one. The trend of these present-day movements corresponds well with uplift of the studied area north of the SMF, which is also indicated by analysis of the drainage network. It is concluded that in areas of low tectonic activity the detailed study of individual characteristics of the drainage network, particularly their spatial relationships, as well as monitoring of fault microdisplacements can reveal rates and kinematics of ongoing tectonism. (C) 2008 Elsevier B.V. All rights reserved.

Monitoring of tectonic movements along three active faults of Dinaric (NW-SE trending) fault system in W Slovenia using TM 71 extensiometers was set up in 2004. After two and a half years of measurements clear trends of displacement were recorded. The average left-lateral displacement along a crack in the inner fault zone of the Idrija fault in Ucja valley was reading 0.38 mm/year. Short term (10 months) rates were even greater and reached the value of 0.54 mm/year. Since the Idrija fault is considered generally to be dextral strike-slipping, the observed left-lateral displacement can be explained by variations in principle stress. Raga fault monitoring site at the foot of Vremscica Mt. established an average reverse uplift of hanging wall (SW) block of 0.24 mm/year and left-lateral displacement of 0.16 mm/year. Short term (9 months) vertical displacements reached the value of 0.53 mm/year. The inclined displacement is in agreement with geological and seismological observations. In the Postojna cave system two instruments were installed at the fault which extends parallely to Predjama fault zone. The average vertical displacement rate at Postojna I site was 0.01 mm/year. Both devices recorded similar reaction which can be attributed to 12 July, 2004 (Mw=5.2) earthquake with an epicentre 70 kin away from the measuring site. Since there were no other stronger earthquakes in the vicinity and time span of monitoring, no other correlations were established with earthquake activity. The observed displacement rates along all three monitored faults of up to 0.5 mm/year are consistent with the regional deformation rate in W Slovenia established from GPS measurements which is of the order of 2 mm/year.

Quaternary faulting in the western part of the Gulf of Corinth has been evidenced by geology and geomorphology, as well as by seismic recording. A series of three main normal fault segments are aligned in a steep southern coastal zone of the gulf These fault segments, 15 to 25 kin long, have an average strike of 90 degrees - 105 degrees and a northward dip of about 50 degrees - 75 degrees. Selected fault points were equipped with 3-D crack gauges TM71 during 2002 to monitor movements along the fault planes here, as well as on another fault cutting through the small island of Trizonia near the opposite northern shore of the gulf. Results of the monitoring present relative displacements induced by active tectonic movements. Generally, the movements recorded on the faults are characteristic of an aseismic linear creep in vertical, i.e. uplifting/subsiding in rates of mm per year due to uplifts of the Peloponnesian Peninsula. In 2003 a three months long period of fast acceleration of movements was recorded. During this acceleration phase displacements changed to skew uplifting/subsiding with a left-lateral horizontal component. Moreover, horizontal rotation of monitored blocks corresponding to a systematic westwards opening of the Gulf was observed with only single eastward opening episodes.