This reply addresses the comment by Vespremeanu-Stroe et al. on our paper which offered broad evidence for the existence of high amplitude vertical displacements at Mangalia, Romania, during the 18th–19th centuries. The comment proposes an alternative storm/tsunami origin for the anomalously elevated marine deposits. We show that the comment relies on weak arguments and is built on unpublished data that cannot be properly evaluated. We systematically rebut these claims, demonstrating that the premise of regional tectonic stability is contradicted by documented seismic activity. The paleoecological interpretation, based on the unproven dominance of a single ostracod genus is unsound, and the proposed storm/overwash scenario is physically implausible. The historically sediment-deprived coast could not have supplied the necessary sand volume for such a deposit. Furthermore, the upwards-coarsening sequence, fine sedimentary structures, and shells found in anatomical connection are diagnostic of nearshore progradation, not high-energy overwash events. The alternative hypothesis also lacks support from historical or meteorological records. We conclude that the neotectonic model of subsidence, infilling, and subsequent uplift remains the most parsimonious explanation for the evidence we found.

Sea level reconstructions in the Black Sea basin and elsewhere rely on the identification of sea level markers and on the understanding of their post-genetic vertical movements. We present here evidence of a fast, bi-directional vertical displacement on the western Black Sea shore at Mangalia, Romania. We argue that an area situated near the shoreline was submerged 4 m, subsequently filled with marine silts and sands, then uplifted by 10 m, where it currently stands. Radiocarbon dating of several types of materials from the infill, as well as archaeological evidence, indicate that this displacement occurred during the eighteenth to nineteenth centuries. Mollusc shells found in anatomical connection close to the top of the sediment sequence have a 14C reservoir age offset of 900 years, probably due to the hard water effect. This is much larger than the 400 year offset that is generally considered for the Black Sea and highlights the problematic dating of Black Sea coastal sediments. The findings of this study offer strong evidence of short-term, local tectonic movements that should be considered when past sea levels are calculated, while at the same time serve a warning for urban and marine development planners.

The Alborz Mountains are among the areas exhibiting high tectonic and seismic activity in northern Iran. Studying key parameters of tectonic structures, including quantitative analysis and observational studies, in such active regions is essential to identify potential active faults and assess the consequent seismic hazards. This study focuses on seismicity and seismotectonics by analyzing seismic parameters, including b-value, mean seismic activity rate, earthquake recurrence time, seismic moment, and fractal dimension derived from micro and teleseismic data. The b-values vary between 0.6 and 1.1 in the tectonically active parts of the study area, corresponding with the reverse/thrust and strike-slip active faults. Large earthquakes might be prone to occur at 10–25 km depth because both catalogues show low b-values (b < 1.0) concentrations at this depth range. The high fractal dimension (> 1.5), high seismic activity rate, large seismic moment parameters, and its continuously increasing trend. Short recurrence periods (20–50 years) of M 6.5 events also emphasize the high seismic activity and high seismic hazard. On the other hand, the prevalence of low b-values is notably observed in areas encompassing densely populated cities such as Rasht, Lahijan, Amol, Babol, Sari, Behshahr, Gorgan, and the megacity of Tehran. Furthermore, we have identified asperities where the Gorgan Plain, the Khazar, and the Alamutrud Fault Zones are located. These findings emphasize the seismic hazard potential in the identified areas and urban centers within the study area. Therefore, particular attention should be directed towards areas exhibiting low b-values when assessing and mitigating seismic hazards. It underscores the necessity for additional focus on seismic hazard assessment and implementation of mitigation strategies in the Alborz region.

Some conceptual models proposed for explaining the Hindu Kush intermediate-depth seismicity assumed that a subhorizontal fracture was migrating laterally, from east toward west, along the strike of a subducted tectonic plate. The present study has identified a distinct cluster of earthquake hypocenters, likely corresponding to the advancing tip of the subhorizontal fracture. Those hypocenters belonged to a set of fairly moderate earthquakes (5.6 <= M <= 6.5), which had not been, so far, explicitly addressed in the Hindu Kush seismo-tectonic interpretations, and which were proven to be virtually the only events displaying a failure regime characteristic to a laterally propagating breakoff - namely, reverse-fault focal mechanisms with subhorizontal compression axes parallel to the slab strike. A separate, upper-positioned hypocenter cluster was noticed to include all the M-w >= 7 intermediate-depth earthquakes: it was conjectured, relying on a previously published numerical model, that those strong events could be triggered by upward transfer of the viscoelastic stress induced by the slab pull increase caused by an episode of lateral breakoff advance. At the same time, as the inferred breakoff fracture enables the deeper segment of the plate to detach from the shallower segment, the plate region situated above the severed region is relieved of the gravitational pull that was imposed by the deeper, and currently detached, plate segment. In response to the resulting crustal rebound, the surface topography is expected to exhibit down-tilting to the west. Such an anticipation seems to be confirmed by the catchments of several streams which flow roughly perpendicular to the intermediate-depth earthquakes epicentral domain: relevant geomorphic indices (the swath profile average and maximum elevation curves; the transverse hypsometric integral - THi; the transverse topographic symmetry factor - T-vector) computed for the concerned valleys consistently suggested larger uplift rates in the east, as compared to those manifest further to the west.

Summary The present paper is focused on municipal solid waste (MSW) deposits, as their management is quite challenging. Landfills are a dynamic system, with continuous modifications at each level, under either aerobic or anaerobic conditions. For improved management of the landfills, both from an economic and environmental perspective, it is useful to know the electrical resistivity distribution of the waste body. The low electrical resistivity values are associated with areas with high leachate content, while the high resistivity ones can be encountered in the case of dry garbage, garbage with low permeability, or with low moisture content. There is a specific interest in knowing the moisture content of the waste deposits, as it is necessary to keep humidity between 35–65% in order to have a good decomposition rate of the organic matter. So, indirectly, the geophysical results can aid in planning the intervention actions (such as leachate recirculation) in bioreactor landfills, by locating areas where is necessary to increase the moisture of the waste as well as to evaluate the leachate content of a landfill.

Summary We focused our research on a north part of the central region of Dambovita County, part of the relief unit known as Subcarpathians of Ialomiţa as severe events of the mass movement were reported during time, but have never been the subject of a detailed investigation with modern techniques. According to the GIS-based risk analysis, the areas that are most prone to landslides are found in the eastern and south-eastern parts of the study area, in the Mercani and Baloiu Hills, where steep slopes are predominant and geology includes schist, flysch, and sandstones. However, the landslide susceptibility model is theoretical, being an approximate prediction of the real dynamic of the actual situation in the study area, given in terms of probability. On the other side, InSAR techniques depict the real past and present dynamics of the surface, by measuring surface displacement. These two techniques can be cross-correlated in a future study for validating the results of the susceptibility model.

Summary Mapping geohazards of various scales, such as earthquakes and landslides, by Interferometric Synthetic Aperture Radar (InSAR) techniques, has been widely used in recent years. Monitoring landslide deformation with InSAR can help us better understand the mass propagation and motion evolution in space and time, respectively, and the driving factors. Saein landslide event in 2005 destroyed at least 350 m of Ardebil-Sarab roadway and power lines. The maximum horizontal and vertical displacement during the landslide were 10–20 m and 7–10 m, respectively. We selected three monitoring points in the study area to perform time-series analysis using the Sentinel-1 wide swath data acquired from 01.01.2019 to 08.04.2021 in descending orbit. In P-1 and P-3, creeping rates vary from +10.5 ± 0.5 to +22.0 ± 1.0 mm/yr and 6.1 ± 0.8 to 24.0 ± 2.0 mm/yr, respectively. Whereas the maximum creeping rates in P-2 are +7.0 ± 1.0 to −40 ± 2.0 mm/yr. The average velocity in P-1, P-2, and P-3 are 1.70, -16.5, and 3.20 mm/yr, respectively. Our results indicate that the existence of crushed zones in volcano-clastic rocks and volcanogenic sedimentary units due to the activity of the Yamchi Fault Zone has reduced stability along the slopes and accelerated creep movements.

FLORINA CHITEA, HORIA MITROFAN, ILIAS FIKOS, IRINA MARILENA STANCIU, CONSTANTIN DIACOPOLOS, RĂSVAN STOCHICI 1 Institute of Geodynamics of the Romanian Academy, Bucharest, Romania 2 Faculty of Geology and Geophysics, University of Bucharest, Romania 3 Exploration Geophysics Laboratory, Aristotle University of Thessaloniki, Greece 4 National Research and Development Institute for Marine Geology and Geo-ecology – GeoEcoMar, Bucharest, Romania

Summary The geophysical survey was performed in the Transylvanian Depression, Romania, in an area where a rare type of mud volcanoes, in terms of the ejected gaseous emissions, is encountered. Despite this interesting phenomenon, there is a lack of geophysical data in the region and their deep structure is unknown. By means of ERT data, there were revealed 2 fault lineaments, one trending W-E and other trending SSW-NNE. Following the direction suggested by the ERT data, evidence for their extent was further investigated by analyzing the saline or brine water samples collected from the region and comparing the corresponding chemical facies with the one displayed by the Homorod mud volcanoes extruded liquid. It was therefore possible to better understand the regional trend of the SSW-NNE fault line.

Methane occurrences displaying signatures of a possible abiotic origin had previously been reported in the South-West Carpathians (Romania). Such an accumulation, at Tisovita, was intercepted by a well drilled in an ophiolitic rocks massif, whereas in two other localities-situated tens of kilometres faraway-the concerned methane is released via thermal groundwater outflows that are apparently not associated with any ultramafic products. By using groundwater ionic compositions, corroborated with previously published isotopic (C-13-CH4,H-2-CH4,He-3/He-4) and molecular gas analyses, we assessed in more detail the conjectured abiotic provenance of methane, and quantitatively investigated the hypothesis of a progressive mixing between two, abiotic and thermogenic, methane end-members. The corresponding geofluids behaviour was modelled by hypothesizing a "concealed" ophiolite serpentinization setting (largely similar to that at Tisovita), whose abiotic methane production was "diverted" towards remote discharges at ground surface, via a similar to 20-km-long flowpath supposedly generated by recently operating extensional tectonics.

Summary Detection of buried remains of old structures is not always an easy target for electrical or electromagnetical methods as sometimes there is a low contrast between buried remains and embedded rocks or due the interference of modern infrastructure which makes difficult to isolate the buried remains signal or limits the deployment of geophysical profiles. In this paper, we present a successful case study, where local geophysical noise sources were overpassed by using ERT method. High-resolution 2D models allowed to locate buried remains of old facilities and even to reconstruct the footprint of an old building which displayed a complex “L” shape. The 3D ERT resulted model allowed to compare different sectors of the building, to extract the most probable foundation structure (different on two wings) and to analyze the construction rubble filling material.

Each of the three major earthquakes (M w ≥ 6.9) recorded within the Vrancea seismogenic body in the years 1977, 1986 and 1990 may have been the result of long-range interactions. The latter seemed to be initiated in coincidence with a moderate (4.7 ≤ m b ≤ 4.9) shock that systematically occurred in the 160–175 km depth-range, 3–4 years in advance of the major earthquake. In addition, each corresponding pair of moderate/major events systematically exhibited, in terms of focal mechanisms, a particular pattern: the latter complied with predictions of a numerical model that had addressed along-strike break-off experienced by a near-vertical slab, which—at the same time—was strongly coupled with its overriding plate along a steeply dipping contact extending on a significant vertical length. It was thus suggested that the Vrancea moderate events of thrust-fault type occurred in the 160–175 km depth-range could correspond to the along-strike propagation of a detachment horizon tip; while the major earthquakes subsequently occurred at shallower depths (85–135 km), were possibly caused by the shearing forces that acted, at the upper-plate/underlying-plate interface, in response to the increased downward pull experienced by the Vrancea slab as the break-off was propagating laterally.

Within a slab experiencing present-day lateral break-off, a particular type of earthquakes is expected to cluster at the detachment horizon tip: namely, events generated by reverse faulting, with the approximately horizontal compression involved acting along the strike of the slab. Such a cluster of moderate magnitude earthquakes (4.7 ≤mb ≤5.0) was identified in this study at the 160–175km dept...

The Harghita Mts are located in the central part of Romania and represent the youngest part of the East Carpathians Neogene-Quaternary magmatic belt. The Ciomadul magmatic structure, situated at the southern end of the Harghita Mts, includes the St. Ana Lake and several isolated domes, Puturosul and Balvanyos representing the easternmost outcropping volcanics.Traces of active post volcanic processes are widespread between Tusnad and Balvanyos localities, mostly represented by mineral groundwater springs (displaying a large variety of chemical characteristics) and moffeta (generated by gas emergences rich in CO2).The special interest in this post volcanic activities is given by the perspective of being used as a tool for economic development of the region, once famous for the curative properties of the mineralized groundwater resources and the abundant number of springs (naturally outcropping or tapped).The possibility to revive the great potential of this area is diminished by the small quantities of mineral groundwater offered by the springs nowadays still active and the unsuccessful wells drilled for mineral water exploitation during the last several decades.Benefiting of the specific low electric resistivity values of mineral groundwater in this post volcanic area (mostly ranging between 0.5 and 15 Omega m) it was recently considered that modern geophysical techniques, such as the Electric Resistivity Tomography (ERT), may contribute to locate underground aquifers bearing higher water resources.ERT survey lines were deployed in the Balvanyos, St. Ana Lake and Mohos Peat Bog areas trending N-S, E-W, NW-SE and NE-SW in an attempt to detect structural features involved in groundwater vertical displacement (faults, fractures, tectonic contacts) or its underground accumulations.The high variability of electric resistivity values illustrated in the ERT cross-sections may be interpreted in terms of groundwater quality, rarely here to be used for domestic consumption, but mostly for various medical treatments.

By conducting a chemical investigation that addressed both major and trace elements dissolved in the mineral waters that discharged on the slopes of the recently extinct (ca. 27-35 ka ago) Ciomadul volcano (East Carpathians, Romania), specific processes undergone by the concerned hydrochemical system have been documented.In terms of trace elements concentrations, it was noticed that the concentrations of Ti, V, Co, Ni and Zn never exceed several tens of ppb in near-neutral waters, while in acid waters they could reach, alternatively, several hundred ppb. Similarly, As, Cr and Pb reached up to several tens of ppb in acid waters, while in near-neutral waters their concentrations never exceeded 5 ppb. As for Cu, it was detected only in some of the acid waters, in concentrations up to almost 100 ppb.It was next possible to refine the image suggested by this pattern, by noticing that between acid and near-neutral outlets that occurred very close (ca. 20 m) to one another, the concentration ratios were similar for most of the major components (Ca, Mg, K), as well as for some of the trace elements (Sr, Rb, Ba), being thus suggested that in both types of discharges, a common parent-water was involved. The near-neutral outlets however appeared to be strongly depleted in base-metals (Ti, V, Co, Ni, Cr, Zn, Pb) as "compared to the acid fluids. The latter likely originate in the oxidation of the H2S fraction contained in gas outflows (rich mostly in CO2) released by a still cooling magma body: the H2S oxidation actually occurs when those magma-derived gas outflows finally reach superficial aquifers of essentially meteoric origin.

In the surroundings of Ciomadul Mountain, located in the southern extremity of the Harghita Mountains, Romania, intense discharge of dry (predominantly CO2, H2S) and wet emissions are known to occur, being an evidence of a deeply settled geothermal system.In this post-volcanic environment, an inventory of the water outflows was recently performed, aiming to update the old existing databases and to better document the permanent sources. The appearance of new (spontaneous) sources as well the dryness of other sources was observed during the monitored period extended over one year, being a phenomenon related to both internal (geological) and external (climate) factors.Despite the fact that Harghita Mountains also host the strongest heat-flow anomaly in Romania and hydrogeological records state the presence of a geothermal aquifer located at 800m depth (intercepted by a borehole in andesitic formations), only 2 sources (tapped water) monitored by the authors were identified to have a temperature overpassing 19 degrees C during the whole year. The highest value (28.5 degrees C) was recorded in the SNAM borehole, whose water upflows from similar to 300m depth.A total number of 37 sources, considered as permanent sources, were selected in order to analyse the time and space variability of post-volcanic activities in the area of Tusnad-Bicsad and Balvanyos. According to their spatial position they were divided into 5 groups: Tusnad area (formed by a group of 6 sources), Hammas-Vallato (grouping 11 sources), Balvanyos I (6 sources), Balvanyos II (5 sources) and Csiszar Cold Baths (9 sources).In terms of pH, the groundwater sources from the analysed area1 are classified as moderate to high acid waters, displaying values from 1.53 (u. pH) to 6.86 (u. pH), while the electrical conductivity parameter shows a wide range of values, between 139 and 50600 mu S/cm. The extreme value of 50600 mu S/cm was reported for a wet mofett, loaded with dissolved salts and with intense CO2 emissions.Physical parameters were further used to analyse the influence of the local tectonic on the area1 spreading of the sources (deployment on preferential alignments) and the possibility of interconnection between the sources upflow paths (based on physic-chemical parameters correlation).