Coastal Relief Research Articles

Late-Holocene changes in vegetation and fire within a forest refuge in the Araripe region, northeastern Brazil

In semi-arid northeastern Brazil, where water is scarce, rainforest refugia can be seen along the coastal relief, where the trade winds bring in humidity from the Atlantic Ocean, or further inland, at the Araripe plateau where water comes from aquifer resurgence. In order to reconstruct past changes in water resurgence and in their associated vegetation types, we analyzed pollen, charcoal, and trace elements from sediment cores collected in the permanent swamps created by the resurgences. Our high temporal resolution analyses show that the vegetation was more sparse and drier than today until 2700 cal yr BP. Between 2700 and 2000 cal yr BP, palm swamp and evergreen forest tree taxa started to expand, suggesting an increase in water resurgence. At 2000 cal yr BP, the moist forest with Mauritia expanded and fire activity changed from mixed to woody fuel particles. During the last 200 cal yr BP, a decrease in the palm tree Mauritia flexuosa, an expansion of Poaceae and an increase in macrocharcoal particles are attributed to an increase in anthropogenic activities in the Araripe Basin. The Late-Holocene climatic trend seen at Araripe mirrors that of eastern Brazil and has controlled the aquifer activity, including during the major droughts that affected the region. This is highly relevant for the application of public policies that rely on the aquifers of Araripe for the 21st century.

CENTRAL PART OF NATURAL COASTAL SYSTEM TENDRA–JARYLGACH, THE BLACK SEA COAST

Problems of Research and Purpose. In the theory of general geomorphology, the section on coastal-marine processes at the genetic contact-zone between Land and Ocean assigns importance to the study of relief associations. One such complex of geomorphologic association on maritime coastlines is the winged-forelands. They consist of interconnected complex capes, active cliffs, typical benches, sandy beaches, and aeolian forms. Wind, sea wave, geobotanical, zoogeographical, geochemical, and other factors contribute to their development. Their morphology and dynamics are determined by lithodynamic interaction under the influence of a unified alongshore sediment flow transport. We conducted a study of one such winged-foreland on the non-tidal Black Sea coast, a classic foreland in "the Tendra–Jarylgach shore system". Practical issues were discussed, and identified development patterns allow for rational natural resource usage, emphasizing the relevance of the topic. Purpose of our scientific work is: Based on the obtained materials, identified patterns, and analyses of the development of the classic winged-foreland "the Tendra–Jarylgach" to determine optimal natural resource usage and ways to preserve the natural resources of the coastal environment. Data and Methods: During our research, we applied route and stationary methods, above-water and underwater methods, field descriptive and instrumental methods, cartographic techniques, geographical comparisons, aerial and space remote sensing, and analytical methods. Instruments for topographic and geodetic work, underwater profiling of the nearshore slope, lithological sampling, and laboratory data processing were used. Profiling of accumulative and abrasional forms of coastal relief, coastal intersections in different parts of the winged foreland, and specific descriptions of photo-reflectance were obtained. Special attention was paid to the efficiency of coastal protective structures on the abrasional front. Basical Results and Comments: The presented materials and their brief discussion revealed that the natural system of the winged-foreland "Tendra–Jarylgach" is a complex coastal-marine system of the physical-geographical subregion level with significant dynamics. All secondary elementary systems within it are closely connected by wave energy and sediment material flows in a unified sediment balance. Therefore, its conservation and the usage of its natural resources require a comprehensive systemic approach based on general-geographical principles. Within "the Tendra–Jarylgach" winged foreland, optimal natural resource utilization is achievable based on the general principles of geography and the fundamentals of coastal studies as an interdisciplinary geographical science. Key components of optimization include: a) adherence to rules and norms regarding anthropogenic pressure on the studied natural system; b) organization of the natural system to maintain high air and sea water quality; c) resistance to abrasive activities of the sea through the implementation of effective, operational engineering-geographical measures; d) preservation of sediment balance, as the creation of sediment mass is an exclusively long-term process, while disturbance is an instantaneous process. The leading source of sediment within the studied coastal-marine system is the abrasional input from coastal cliffs and benches. A minor contribution comes as a carbonate material. The coastal zone here experiences a significant deficit of coastal sediments, actively supporting further shoreline erosion. The development of the natural system of the researched winged-foreland is driven by the active action of the unified Tendra–Jarylgach alongshore sediment transport, involving the contribution of shell-detritus. This significantly distinguishes this type of foreland from others where two branches of sediment transport flows in opposite directions from the middle of the frontal part. During particularly strong storms, up to 5% of repetitions on accumulative forms typically result in new inlets and the expansion of existing old breaches. This undermines the stability of both spits, and the entire winged foreland in total. Such negative phenomena are exacerbated by disturbances to the sediment balance, especially artificial removals of beach sands for construction purposes.

Influence of Modern Geodynamic Processes on the Formation of the Coastal Relief and Seabed of the White Sea

Influence of Modern Geodynamic Processes on the Formation of the Coastal Relief and Seabed of the White Sea

Comparison of coastal vulnerability assessment for Subang Regency in North Coast West Java-Indonesia

Coastal vulnerability is a spatial concept that can contributes to decision-making processes in managing the coast. Our study aims to compare and evaluate the coastal vulnerability index (CVI) and the weighted CVI (CVIw) along the Subang Regency coastline in northern part of Java Island-Indonesia. We use coastal parameters: coastal relief, morphology, shoreline change, tidal range, sea-level change, wave height, land subsidence, and land use. Then, vulnerability maps are prepared to highlight areas with low, medium, high, and very high vulnerability. The vulnerability parameters map showed that shoreline change, land subsidence, and land use are influencing the vulnerability more than other parameters. The CVIw appears to be more favourable to assess the Subang Coast vulnerability, in which the very high vulnerability (43%) is dominant compared to the CVI (21%). This will require urgent protective action from the coast managers. Both CVI and CVIw have a 21% of very high risk in the same areas (Mayangan, Legon Wetan, and Pangarengan Villages), and these areas need protection from the coastal land loss. Meanwhile, the authority has plans for aquaculture in the area, and we suggest that it should be planned thoroughly to ensure that the practice does not destruct the coasts any further.

Corrigendum: Recency of Faulting and Subsurface Architecture of the San Diego Bay Pull-Apart Basin, California, USA

Figure 13. Regional fault orientations and plate boundary parameters used for kinematic analysis and interpretation. Solid orange arrows are maximum and minimum horizontal stress orientations, ! and " , respectively (Hardebeck and Hauksson, 2001), large black and white outlined arrows are plate motion vectors, and the average orientations for Group-1, Group-2, and La Nacion fault zones are solid black, toothed lines. Large black hatched lines are regional faults. G1, Group 1; G2, Group 2. Background fault traces (thin red lines) are from USGS Quaternary fault database (USGS, 2019). Background topography and bathymetry are from the National Centers for Environmental Information Southern California Coastal Relief Model (v2) (Calsbeek et al., 2013).

Kompleksnoye issledovaniye volnovykh i litodinamicheskikh protsessov v beregovoy zone p. Morskoye (Vostochnyy Krym)

Wind waves can have a significant impact on the coastal infrastructure. The paper aims at a comprehensive study of regional characteristics of wind waves near the village of Morskoye (south-eastern coast of Crimea), which are necessary to develop a project of reconstruction of the highway adjacent to the coastal area. Space images and cartographic information were used to study the beach dynamics in the studied area. It is shown that before construction of the coast protection structures the beach width in the studied area was 25–30 m, whereas after the construction it narrowed down to 15–25 m. Based on the wind wave reanalysis data obtained using SWAN spectral model and ERA-Interim surface wind fields for 1979–2017, regime characteristics of waves in the coastal zone of Morskoye were calculated. It was found that waves with average periods of 3.0–3.5 s have the maximum recurrence (over 16 %). Wind waves coming from SE-SSE sector have the highest recurrence rate. Estimates were obtained for the extreme characteristics of wind waves that may occur once in a given number of years. The SWASH hydrodynamic model was used to perform mathematical modelling of wave run-up on the coastal area. In their calculations the authors used a regular grid of the coastal relief with high spatial resolution based on the interpolation of topo-geodetic and bathymetric survey results. An incoming wave was given as a soliton of 2.0; 3.0 and 3.4 m high. It was found that with the incoming wave height of 2.0 m, the vertical wave splash in the studied area varies within 1.7–2.2 m. At a height of 3.4 m, the splash reaches 1.8–2.9 m. In this case the beach is flooded completely. During the run-up, wave current velocity amounts up to 5 m/s. Along the lower boundary of the cliff the bottom maximum current velocity reaches 1.5–1.75 m/s. At such velocities near the cliff, the beach consisting of material with the grain size up to 60–90 mm can be eroded.

Geomorphological engineering studies of anthropogenic variability of relief in the marine coastal zone

With the development of the coastal zone and the development of the urbanization process, coastal engineering poses a serious threat to local ecosystems. Poorly designed coastal engineering will have irreversible consequences for local ecosystems, such as loss of biodiversity, loss of connectivity and overall degradation of ecosystems. Therefore, it is imperative to improve the concept of ecosystem design of coastal infrastructure. One of the most important problems of marine engineering geomorphology is the drift of approach channels and changes in the coastal relief. These phenomena are a manifestation of a single process of sediment movement along the coast. The main deformations of the relief, as a rule, are determined by the features of the transverse structure of the alongshore sediment flow. This study discussed the methodology for calculating the movement of sediments, the transformation of the relief of the coastal zone. Regional examples show in general terms the assessment of the drift rate of different channels and different sections of individual channels. The problem of drift and artificial deepening of approach channels of ports is highlighted on the example of the coastal zones of the Baltic Sea. In general, these studies can contribute to improving the development of ecosystem coastal engineering.

Названия берега и форм берегового рельефа в говорах Костромской области: ландшафтно-географический аспект

One of the most detailed systems of terms in regional dialect systems of the language is the terminology of rivers and river valleys, lakes and lake basins. We explore the repertoire of folk geographical terms used in the patois of the Kostroma Region, which are associated with such part of the river valley as the coast. We analyze language units, on the one hand, in the coordinates of the lexical and semantic group, on the other, in relation to the designated objects. We identify the correspondence of terms and their semantics to the nominated forms of coastal relief. In the plan “Program of collecting information for the lexical atlas of Russian folk patois” we consider the general names of the coast and the names that actualize its morphological characteristics – the names of low, low-level and high steep coast, the names of coastal relief forms, such as a cape and a sandbank. At the lexical and semantic level, we trace the connection of local names with the terminological system of the geographical landscape. The repertoire of the terms group under consideration includes mainly words with a transparent inner form, their semantics reflect the features of the coastal relief. At the same time, in the Kostroma Region’s patois, words of obscure origin are encountered, which can be attributed to the substrate vocabulary. In general, the nomenclature of the terms under consideration fits into the concept of the vocabulary continuity of the Kostroma patois.

High-resolution wind speed modeling, and an assessment of mesoscale peculiarities caused by coastline parameters and relief of near-shore Kara Sea regions

Complex shorelines and coastal relief strongly influence wind speeds. Since the Arctic is poorly covered by ground observations, one of the most reasonable approaches to investigating these events is hydrodynamical high-resolution modeling. In this work we apply a model COSMO-CLM to reproduce wind fields and characteristics in different rugged shore conditions. Some model experiments are designed with this regional climate non-hydrostatic atmospheric model COSMO-CLM to investigate the best configuration to reproduce the mesoscale circulations in the Arctic coastal zones considering different relief conditions on the example of the Kara Sea. Some mid-term experiments of a three-month timespan, Aug-Oct of 2012 and Jul-Sep of 2014, are conducted over the Arctic domain and specially over the Kara Sea region using a downscaling approach with ∼12 and ∼3 km horizontal grids. These periods are characterized by some storm events. The purpose of these experiments is to reproduce the surface wind and wave characteristics in the best way, especially near the shorelines during the storm events. Verification of these experiments has shown the best configuration of the COSMO-CLM with a “spectral nudging” technique and reducing the model time step. However, the verification and detailed investigation of the model runs raise a question about the quality of this verification, and how relevant are the wind station data in different coastline and relief conditions. Therefore, an additional analysis is carried out from a synoptic overview of the influence of the coastline configuration on different mesoscales and for different regions. Malye Karmakuly (Novaya Zemlya island), Belyi and Dikson Islands are considered as different examples to study the wind and wave regimes. Although the model cannot describe the dynamics on all scales using a 3-km resolution, it can realistically simulate the islands’ wind shadows, tip jets, downslope winds, vortex chains, etc. on different scales. It justifies further research to apply a finer resolution to learn detailed properties of mesoscale circulations and extreme winds. This analysis has shown a need to predict better these circulations by using numerical modelling.

海岸救援者における「事故防止」の中で対峙する心理的負担感

海岸救援者における「事故防止」の中で対峙する心理的負担感

Lower to middle pleistocene coastal dune fields formation in the western mediterranean (Western Eivissa, Balearic archipelago): Chronology and landscape evolution

Abstract Colluvial and aeolian successions in coastal environments are useful indicators of geomorphological changes that occurred during the Quaternary. Pleistocene aeolian deposits interbedded with colluvial deposits and palaeosols in areas of Cap Negret, Punta de sa Pedrera, Cala Bassa and Cala Compte, western coast of the island of Eivissa (western Mediterranean) are studied here. These deposits span almost continuously along 14 km of the coast, covering an area of approximately 22 km2. We present a sedimentological and stratigraphical description of these Pleistocene outcrops. Five major sedimentary facies involving the succession of aeolian, colluvial and edaphic environments are described. Carbonate sandstones, breccias, conglomerates and fine-grained deposits are the main components of these sequences. Optically stimulated luminescence (OSL) dating of aeolian levels indicates that deposition took place from the Lower to Middle Pleistocene. The sedimentological and chronological analysis of these deposits allows reconstructing of the coastal Pleistocene environmental history from Marine Isotopic Stage (MIS) 22 to MIS 6. Results show that the main controls on Lower to Middle Pleistocene coastal landscape evolution on Western Eivissa are changes in the average wind direction over time, modulated by the interaction with coastal relief orientation. The main episodes of aeolian activity identified and dune formation in the Western Mediterranean can be linked to periods of low sea level.

Incorporating natural habitats into coastal risk assessment frameworks

The coastal risk assessment (CRA) has important implications for policy development, resilience enhancement, and risk reduction to reduce the magnitude and likelihood of future losses to coastal hazards. However, few if any existing in-practice CRA approaches account for the effects of coastal natural habitats (CNHs), which shield communities from natural hazards and support resilience enhancement in coastal regions. Here, we use a coupled human-nature system-based CRA framework to provide evidence on the influence of CNHs on coastal storm-risk levels and spatial distributions. We calculate a risk index for each coastal county along the U.S. Atlantic coast and employ different spatial assessment approaches to systematically analyse the risk. This index incorporates several bio-geo-physical variables (e.g., geomorphology, natural habitats, coastal relief, and historical data on sea level trends, wind, and wave) and data on socio-ecological systems. The index is calculated under two CNH scenarios (i.e., without- and with-habitat) and is further used for mapping the at-risk population. We find that the without-habitat scenario overestimates the population in the highest risk category by 10 % and the number of counties by as much as 40 % as compared to the with-habitat scenario—mostly in the Gulf region. Also, the without-habitat scenario miscalculates the spatial distribution of the risk (e.g., over/under-estimate the relative risk for Florida/New York). These findings highlight the role of CNHs to provide defensive services and the importance of incorporating CNHs into the risk assessment process. While the CNHs inclusive risk results are important for coastal risk-reduction through prioritization and smart resource allocation, the well evident influence of CNHs on risk level and its distribution is also supportive for conservationists to stress the policies relevant to the protection and restoration of coastal natural systems owing to their multiple services.

Coastal dynamics in the Narva bay of the Baltic sea: present-day state and development tendencies

Central part of Narva bay is characterized by accretive coast, which is formed due to the presence of significant volumes of sand deposits. In the paper, the current state of coastal relief was analyzed and the forecast of its evolution under the prevailing wave climate was performed. The problem of the equilibrium of the coastal morphosystem for a given sediment budget and the probable trend of relative sea level was considered. Morphodynamic forecast for the period of the next decades was justified for designing the crossing of the coastal zone by the main pipeline route. Increasing of the role of accumulation processes from the south to the north has been identified through the field survey and analysis of satellite images, and has been shown by the nature of the beach relief and the underwater coastal slope. The calculation of the longshore sediment drift revealed the existence of a convergence zone for two differently directed sediment flows. Convergence of the sediment flows leads to accumulation of sand deposits at the rate of 19.0 m3 per one running meter per year. Estimates of the sediment budget resulted in the estimation of the accumulation rate at 8 m3 per one running meter per year in the coastal zone of area of the pipeline route. Sand accumulation leads to coastal accretion at the rate of 1 m per year. The obtained results lead to the conclusion on the stability of the coast in the coming decades unless the change of the sources of sand sediments and tendencies of its transport.

Geomorphological Processes and Environmental Interpretation at Espalmador islet (Western Mediterranean)

This study presents a sedimentological and stratigraphical description of the Pleistocene deposits cropping out in Espalmador islet (Illes Pitiüses). Four major sedimentary facies including the succession of aeolian, marine, colluvial and edaphic environments are described. The sedimentological and stratigraphical analysis of these deposits allows the reconstruction of the coastal Pleistocene environmental and geomorphological history of the Espalmador islet. The coastal relief and the fluctuations of the sea level mainly control the Pleistocene coastal landscape evolution on Espalmador. Episodes of aeolian activity and dune formation related to a predominant northwestern wind direction can be linked to periods of low sea level where a high amount of marine sediment is exposed on the shelf platform.

Best Practices for Elevation-Based Assessments of Sea-Level Rise and Coastal Flooding Exposure

Elevation data are critical for assessments of sea-level rise and coastal flooding exposure. Previous research has demonstrated that the quality of data used in elevation-based assessments must be well understood and applied to properly model potential impacts. The cumulative vertical uncertainty of the input elevation data substantially controls the minimum increments of sea-level rise and the minimum planning horizons that can be effectively used in assessments. For regional, continental, or global assessments, several digital elevation models (DEMs) are available for the required topographic information to project potential impacts of increased coastal water levels, whether a simple inundation model is used or a more complex process-based or probabilistic model is employed. When properly characterized, the vertical accuracy of the DEM can be used to report assessment results with the uncertainty stated in terms of a specific confidence level or likelihood category. An accuracy evaluation has been conducted of global DEMs to quantify their inherent vertical uncertainty to demonstrate how accuracy information should be considered when planning and implementing a sea-level rise or coastal flooding assessment. The evaluation approach includes comparison of the DEMs with high-accuracy geodetic control points as the independent reference data over a variety of coastal relief settings. The global DEMs evaluated include SRTM, ASTER GDEM, ALOS World 3D, TanDEM-X, NASADEM, and MERIT. High-resolution, high-accuracy DEM sources, such as airborne lidar and stereo imagery, are also included to give context to the results from the global DEMs. The accuracy characterization results show that current global DEMs are not adequate for high confidence mapping of exposure to fine increments (< 1 m) of sea-level rise or with shorter planning horizons (< 100 years), but they are suitable for general delineation of low elevation coastal zones. In addition to the best practice of rigorous accounting for vertical uncertainty, other recommended procedures are presented for delineation of different types of impact areas (marine and groundwater inundation) and use of regional relative sea-level rise scenarios. The requirement remains for a freely available, high-accuracy, high-resolution global elevation model that supports quantitative sea-level rise and coastal inundation assessments at high confidence levels.

The record of postglacial environmental changes of the southern Baltic coastal zone in the sequence of fossil soils

PurposeThe studies aimed to reconstruct major phases of litho-morpho-pedogenic processes and past environmental changes in the Baltic coastal zone near Poddąbie (54°37,070′ N, 16°57,897′ E) based on physical, chemical, pollen, and fossil Cladocera analysis of the polycyclic pedocomplex.Materials and methodsThe polycyclic pedocomplex under study included seven fossil soils developed from the Early Holocene until modern times from various materials. The soils were sampled and analyzed using standard procedures in soil science to determine their physical and chemical properties. Pollen and fossil Cladocera analysis was also carried out in the examined profile. Radiocarbon dates of selected samples were also specified.Results and discussionThe studied polycyclic pedocomplex has been developed from materials of varied origin, including glaciofluvial, fluvial, aeolian, and biogenic deposits of the lake. According to the results of pollen and fossil Cladocera analysis and radiocarbon dating, this body of water has evolved from the beginning of Preboreal period to the half of Boreal. The studied soils represent various reference groups and advancement of development. They constitute relics of former geomorphological and soil-forming processes, which have taken place over the last 9500 years, including periglacial processes, wildfires, Baltic Sea shoreline changes, and aeolian activity. The last stage of the coastal relief dynamics was conditioned by the fire which took place about 1472–1637 AD. The lack of plant cover and intensive abrasion due to direct vicinity of the coastline has caused the deposition of aeolian material, which is the parent material of nutrient-poor initial soils.ConclusionsThe analysis of fossil soil development with the use of specialized research methods allowed for reconstructing the dynamics of past geomorphological processes and natural environment changes in the study area. The studied polycyclic pedocomplex constitutes a record of environmental changes taking place in the central part of the Polish Baltic coastal zone from the Early Holocene to the present day. The studied soil sequence is located within a land depression developed in place of the former water reservoir created as a result of permafrost degradation, and filled with Holocene deposits.

Coastal dynamics of the eastern Gulf of Finland, the Baltic Sea: toward a quantitative assessment

The easternmost part of the Gulf of Finland is characterized by intense coastal processes dominated by wave erosion. Reliable prediction of the coastal zone development, as well as effective strategy for coastal protection, demands a quantitative assessment of beach transformation and volume of sediment loss as a result of extreme storms. The main goal of this study based on results of terrestrial laser scanning was to establish volumes of eroded, transported, and redeposited sand during storm surge events that occurred between 2012 and 2017, and to verify a mathematical model of beach profile changes within key areas located in the Kurortny District of St. Petersburg (Gulf of Finland, Baltic Sea), where the longest set of levelling and terrestrial laser scanning was conducted. The resulting detailed 3D GIS models of coastal relief, based on high-resolution geodesic surveys, produced a highly reliable database of beachface transformation under the extreme storm impact and quantitative assessment of erosion volumes and sediment loss.

A distributed approach for calculating inundation height based on Dijkstra's algorithm

AbstractThis research proposed a parallelized approach to scaling up the calculation of inundation height, the minimum sea‐level rise required to inundate a cell on a digital elevation model, which is based on Dijkstra's algorithm for shortest‐path calculations on a graph. Our approach is based on the concepts of spatial decomposition, calculate‐and‐correct, and a master/worker parallelization paradigm. The approach was tested using the U.S. Coastal Relief Model (CRM) dataset from the National Geophysical Data Center on a multicore desktop computer and various supercomputing resources through the U.S. Extreme Science and Engineering Discovery Environment (XSEDE) program. Our parallel implementation not only enables computations that were larger than previously possible, but also significantly outperforms serial implementations with respect to running time and memory footprint as the number of processing cores increases. The efficiency of the scalability seemed to be tied to tile size and flattened out at a certain number of workers.

Coastal Typology of Landform in Pelabuhan Ratu Bay, Sukabumi Regency, Jawa Barat Province

Sukabumi Regency has potential tourism sector which encourage the use of beach attractions in Pelabuhan Ratu Bay. The main tourist attraction is the hilly and plain panorama beach. This study is aimed to analyze landform and coastal typology to support coastal tourism development. This research provides overlay method of height and slope map, field observation, and verification. Identification of coastal typology was based on coastal materials (rock types and structures), relief (slopes and altitudes), and genesis. Comparative and descriptive spatial analysis were used as method of analysis. The result showed that the coastal typology of landform of Pelabuhan Ratu Bay consisted of volcanic, marine deposition, and organic coast. The beaches such as Cibareno, Cibangban, Karang Naya, Kadaka, and Loji have volcanic coast landform with flat, wavy, sandy, rocky beach typologies. The beaches in Pelabuhan Ratu sub-district, such as Citepus, Gado Bangkong, and Karang Pamulang, have landform of marine deposition with flat and sandy beach typology. Karang Haji and Karang Hawu beaches are coral reef organic beaches. Meanwhile, estuaries were found in Cikakak estuary and Cimaja beaches. The existence of beach tourism in Pelabuhan Ratu Bay is dominated by rocky sandy beaches and flat reliefs strongly support the development of coastal ecotourism.

Synchronization of Long Ocean Waves by Coastal Relief on the Southeast Shelf of Sakhalin Island

The phenomenon of synchronization (trapping) of coming waves by the resonant water area in a coastal zone of the sea found from the observed data is considered in the paper. Edge waves with the period of about 10.7 minutes are visually observed in sea level fluctuations near the village of Okhotskoye and the cape Ostri on the southeast coast of Sakhalin Island. These waves are synchronized with the resonance water area. It becomes apparent from the unlimited increase of a phase between the bottom stations installed at distance of about 7.5[Formula: see text]km. In relation to the phenomenon found, the problem of weak and periodic impact on regular self-oscillatory system — Van der Paul’s oscillator — is considered. Good compliance between theoretical model and data of experiments is obtained.