Distant Earthquakes Research Articles

Sources of seismic noise in an open-pit mining environment

We present the characterization of the sources of vibration in the open-pit Riotinto mine (southern Spain), based on the data recorded by a dense seismic network of 30 stations located along a 1-km long segment of a tailings dam. We describe the most common transient signals detected, including local and distant earthquakes, blasting and vehicles. The time variations in the amplitude of the 10–40 Hz frequency band are then used to define three phases of activity during the recording period. The phase with the highest seismic amplitudes is observed during a time interval of five weeks, coinciding with the civil works carried out for the regrowth of the dam, necessary to correctly capture the continuously increasing amount of tailings. In the last three months of operation of our network, the seismic noise is dominated by the deposition of tailings into the pond, enabling the use of seismic data to monitor into detail the evolution of the deposition process.

The suitability of various recording methods and devices for registration of seismic signals

Analytical study and summarization of dynamic and frequency characteristics of the seismic-acoustic vibrations originated by the near and distant earthquakes and other natural and artificial seismic processes, as well as information analyses of their duration and repetition were done. These allow the formulation of appropriate technical requirements for seismic recording devices, as well as to analyze and evaluate the possibilities of implementing various methods and devices for recording signals from different seismic-acoustic processes depending also on the seismological and other tasks to be solved and various additional specific requirements.It has been shown, that although the introduction of various methods and devices for the digital recording of seismic signals substantially increased during the last decades in seismology, however, it is not even possible to record seismic signals in their entire possible amplitude-frequency ranges employing a single digital recording device too.It also has been confirmed that the widespread usage of digital recording, transmission, machine processing, and analyzing of seismic signals in most contemporary seismic stations does not reduce the value and does not eliminate the need, but, on the contrary, assumes the conduction of simultaneous analog visible registration of seismic processes to obtain express controlling visible records, provide operational manual express analysis of seismograms.

Исследования математических моделей процессов деформаций зданий и сооружений

Purpose. The article is aimed at analyzing changes in the dynamic characteristics of a building and establishing the dependence of shear deformation accelerations on the building's storey to predict the effect of seismic vibrations on the technical condition of the building, taking into account the engineering and geological properties of the foundation. Methodology. A number of instrumental observations using geodetic devices, automated monitoring systems and engineering seismic stations were made to study the issues of assessing changes in the dynamic characteristics of high-rise buildings and structures. To create mathematical models of deformation processes of buildings and structures, the study of interaction of structural elements of the building with the engineering-geological structure of the ground in the upper and lower parts of the megapolis was proposed. Findings. The results on ground shaking intensity acceleration, effective duration, spectral coefficients and periods of spectrum maximum are obtained. The results of measurements of vibrations on different floors of a high-rise building based on instrumental records of seismic station of local and distant earthquake have been obtained. Dependences of accelerations of shear deformations on the floor of the building with regard to engineering-geological properties of the base have been established. Predictive models of deformation processes of the building taking into account dynamic characteristics of ground vibrations and energy class of earth crust movements have been proposed. Originality. The analytical technique of correlation analysis of random variables is proposed, by means of which normally distributed linear and nonlinear processes are studied to create a mathematical model of deformation processes of buildings of different storeys. Practical value. The obtained results of the study of deformation processes of buildings and their structural elements allow to predict the dynamic model of the process of displacements of points of the structure taking into account the dynamic characteristics of ground vibrations and energy class movements of the Earth's crust

Costa Rican Faults Quiver in Response to Distant Earthquakes

Scientists found flurries of seismic activity within weak fault zones in Costa Rica after two giant ruptures elsewhere.

Large, distant earthquakes can trigger microseismicity in Costa Rica

Large, distant earthquakes can trigger microseismicity in Costa Rica

Seismic microzoning in Novi Sad, Serbia – A case study in a low-seismicity region that is exposed to large and distant earthquakes

Seismic microzoning in Novi Sad, Serbia – A case study in a low-seismicity region that is exposed to large and distant earthquakes

Stress transfer outpaces injection-induced aseismic slip and triggers seismicity

As concerns rise over damaging earthquakes related to industrial activities such as hydraulic fracturing, geothermal energy extraction and wastewater disposal, it is essential to understand how subsurface fluid injection triggers seismicity even in distant regions where pore pressure diffusion cannot reach. Previous studies suggested long-range poroelastic stressing and aseismic slip as potential triggering mechanisms. In this study, we show that significant stress transfer far ahead of injection-induced aseismic slip can travel at much higher speeds and is a viable mechanism for distant earthquake triggering. It could also explain seismicity migration that is much faster than aseismic slip front propagation. We demonstrate the application of these concepts with seismicity triggered by hydraulic fracturing operations in Weiyuan shale gas field, China. The speed of stress transfer is dependent on the background stress level and injection rate, and can be almost an order of magnitude higher than that of the aseismic slip front.

Identifying attacks in the Russia-Ukraine conflict using seismic array data.

Seismometers are generally used by the research community to study local or distant earthquakes, but seismograms also contain critical observations from regional1,2 and global explosions3, which can be used to better understand conflicts and identify potential breaches of international law. Although seismic, infrasound and hydroacoustic technology is used by the International Monitoring System4 to monitor nuclear explosions as part of the Comprehensive Nuclear-Test-Ban Treaty, the detection and location of lower-yield military attacks requires a network of sensors much closer to the source of the explosions. Obtaining comprehensive and objective data that can be used to effectively monitor an active conflict zone therefore remains a substantial challenge. Here we show how seismic waves generated by explosions in northern Ukraine and recorded by a local network of seismometers can be used to automatically identify individual attacks in close to real time, providing an unprecedented view of an active conflict zone. Between February and November 2022, we observed more than 1,200 explosions from the Kyiv, Zhytomyr and Chernihiv provinces, providing accurate origin times, locations and magnitudes. We identify a range of seismoacoustic signals associated with various types of military attack, with the resulting catalogue of explosions far exceeding the number of publicly reported attacks. Our results demonstrate that seismic data can be an effective tool for objective monitoring of a continuing conflict, providing invaluable information about potential breaches of international law.

River thorium concentrations can record bedrock fracture processes including some triggered by distant seismic events

Fractures are integral to the hydrology and geochemistry of watersheds, but our understanding of fracture dynamics is very limited because of the challenge of monitoring the subsurface. Here we provide evidence that long-term, high-frequency measurements of the river concentration of the ultra-trace element thorium (Th) can provide a signature of bedrock fracture processes spanning neighboring watersheds in Colorado. River Th concentrations show abrupt (subdaily) excursions and biexponential decay with approximately 1-day and 1-week time constants, concentration patterns that are distinct from all other solutes except beryllium and arsenic. The patterns are uncorrelated with daily precipitation records or seasonal trends in atmospheric deposition. Groundwater Th analyses are consistent with bedrock release and dilution upon mixing with river water. Most Th excursions have no seismic signatures that are detectable 50 km from the site, suggesting the Th concentrations can reveal aseismic fracture or fault events. We find, however, a weak statistical correlation between Th and seismic motion caused by distant earthquakes, possibly the first chemical signature of dynamic earthquake triggering, a phenomenon previously identified only through geophysical methods.

Hydrogeological Responses to Distant Earthquakes in Aseismic Region

For the first time precise measurements of the groundwater level variations in the territory of the Mikhnevo geophysical observatory in an aseismic region (Moscow region, Russia) have been carried out since February 2008 at a sampling rate of 1 Hz. The groundwater level variations under quasi-stationary filtration are considered indicators of the dynamic deformation of a fluid-saturated reservoir represented by carbonate-terrigenous sediments. Both permanent (long-term) factors—atmospheric pressure, lunar-solar tides, and periodic (short-term) ones—seismic impacts from distant earthquakes, are used as probing signals for analyzing the filtration parameters of aquifers of different ages. Hydrogeological responses to the passage of seismic waves from earthquakes with magnitudes of 6.1–9.1 with epicentral distances of 1456–16,553 km was recorded in 2010–2023. Dependences of dynamic variations of the pore pressure in the upper weakly confined and lower confined aquifers on the ground velocity are approximated by different regression functions. Spectral analysis of hydrogeological responses made it possible to identify coseismic and postseismic effects from distant earthquakes. The postseismic effects in the form of an episodic increase in the pore pressure may be caused by a skin effect—clogging of microcracks nearby the wellbore by colloidal particles under intensive seismic impact.

Continents never forget: seismological record of lithospheric deformation 1 billion years ago

Abstract A seismic array extended from the Grenville Province into the Abitibi and Opatica subprovinces of the Superior Province, Canada. We use P-to-S converted waves in seismograms of distant earthquakes to probe boundaries in seismic properties, and demonstrate the presence of a prominent seismic feature that dips NNW into the mantle beneath the Grenville Front. We use two variants of receiver function (RF) analysis, a common conversion-point (CCP) imaging that combines seismic signals from multiple paths connecting sources and receivers, and harmonic decomposition of RF data that separates signals according to their direction in the cone of paths from which the signals have come. CCP images show the crust beneath the Grenville Province to be thicker than beneath the Superior Province, and identify a NNW-dipping boundary beneath the Grenville Front. Harmonic RF analysis shows that this feature is associated with seismic anisotropy in upper-mantle peridotite, and that this anisotropic feature extends to depths of at least 70 km. We interpret the feature as the result of a NNW-dipping shear zone formed within the mantle lithosphere during the Grenvillian continental collision. It could have accommodated internal deformation within Laurentian lithosphere or, more speculatively, mark the contact with the impacting Amazonian lithosphere.

Earthquake-Induced Tsunamis in Western Greece (Ionian Sea and Western and Southern Peloponnese): Use of Tsunami Quantities, Impact and ITIS-2012 Intensities for Highlighting Susceptible Areas

Taking into account recent studies on the tsunamigenic potential of strike-slip faults, it is concluded that there is a need to reassess their near-source tsunami hazard and risk. One of the areas which needs reassessment is Western Greece, especially the Ionian Islands and the western coastal Peloponnese, where major seismogenic strike-slip structures occur. In this context, an extensive review of the available literature is conducted, including not only earthquake and tsunami catalogues but also tsunamis’ imprints on the stratigraphic record. It is concluded that the Ionian Islands and the western Peloponnese have a rich history of tsunamis since 6000 BC, revealing that they are subjected to high tsunami hazard. In addition to the teletsunami effects of distant earthquakes, there are also local tsunamis with smaller physical quantities and slighter coastal impact that are attributed mainly to local offshore faults and earthquake-triggered landslides. The fact that no destructive local tsunamis have been detected so far does not exclude the possibility of future triggering. In order to identify areas susceptible to future tsunami impact, we extract tsunami quantities and coastal impact data from available sources and we apply the Integrated Tsunami Intensity Scale 2012 (ITIS-2012) for all the events with available and adequate information. The highly susceptible areas comprise straits, funnel-shaped bays and extensive coastal areas exposed to major strike-slip seismogenic sources in the Ionian Sea and the western Hellenic Trench. Based on the aforementioned information, the inclusion of the Ionian Sea in the tsunamigenic zones of Greece is strongly recommended.

Simulation and Soft Computation on Materials Prognostication Seismic Assessment

The research paper ETABS is an integrated programming software providing mass distribution and rapid analysis of structures building where we can assign loadings per codal provision. Different methods are also available to elongate our research and analysis of the system. This software developed by CSI is also utilized in the designing of Burj khalifa. ETABS is coordinated programming giving mass dispersion and immediate investigation of building designs where one can allocate loadings according to any codal arrangement. Various strategies are additionally accessible to extend our examination and examination of construction. This paper depicts to determines the role of dampers in tall structures. To assess the stability of the system under seismic load considering dampers. To compare two distinct types of dampers to evaluate the seismic effect of different earthquakes. To provide cost analysis of form per SOR to assess the seismic impact on distant earthquakes.

Violent Groundwater Eruption Triggered by a Distant Earthquake

AbstractIt is now well established that earthquakes cause various hydrogeological responses at distances thousands of kilometers from the epicenter. What remains unexplained is the large amplitude and intensity of some responses. Following the 2004 Mw 9.1 Sumatra earthquake, groundwater 3,200 km from the epicenter erupted violently from a well and formed a water fountain reaching a height exceeding 60 m. We model the relevant processes by combining tidal analysis of groundwater level with numerical simulations using a two‐dimensional finite‐element model. We suggest that the eruption resulted from a combination of factors, including a rapid increase of crustal permeability and runaway CO2 exsolution and bubble nucleation induced by the passage of seismic waves. Our results may have implications for some engineering applications such as oil production and CO2 sequestration, and the eruption of hydrothermal features such as geysers.

Potential triggers for large earthquakes in open‐pit mines: A case study from Kuzbass, Siberia

AbstractThe extraction and movement of rock during mining operations is considered a possible trigger for slip along the fault. In this study, possible anthropogenic causes were analyzed for triggering the earthquake with the local magnitude of ML = 6.1 (at a depth of 4 km just beneath the quarry), in the vicinity of the large coal open‐pit mine in Russia. This event was the largest earthquake associated with a quarry (an open pit). A sufficiently deep occurrence of the source testified that seismic vibrations were produced in a dynamic slip along a preexisting and prestressed tectonic fault. Analytical calculations were conducted of increments of normal and shear stresses at fault planes with several dip angles at depths corresponding to the probable location of the hypocenter of the Bachat earthquake. As the results show, long‐term rock excavations bring a prestressed thrust fault closer to the ultimate Coulomb strength, and stress variations at those depths may suffice to initiate a movement along the fault. By measuring seismic vibrations at different quarries and mines in Russia, the dynamic effect at the supposed depth of the source occurrence could be reliably estimated. As is shown, the ultimate anticipated dynamic deformations are noticeably lower than corresponding values produced by seismic waves of distant earthquakes in the case when the effects of dynamic triggering were observed. Accordingly, the seismic effect of explosions cannot trigger a large earthquake with deep source occurrence. Operations in open‐pit mines can only bring forward the moment of an earthquake at a potentially seismogenic fault. At the same time, the numerical calculations reveal that a branching network of underground tunnels located at several horizons can noticeably reduce the effective shear modulus of the host rock. This effect can even provoke a dynamic movement at a previously aseismic fault.

Analysis of Local Site Effects in the Međimurje Region (North Croatia) and Its Consequences Related to Historical and Recent Earthquakes

The Međimurje region (North Croatia), situated between the Drava and Mura rivers with a slightly elevated hilly area, can be generally characterized as a low-seismicity area. However, macroseismic observations from historical and recent earthquakes indicate that some localities in this region are more prone to damage than others. Significant damage and the observed higher intensities in the Međimurje region after the historical earthquakes of 1738 MLm5.1 (Međimurje) and 1880 ML6.3 (Zagreb), and events that occurred in the instrumental era, 1938 ML5.6 (Koprivnica), 1982 ML4.5 (Ivanec), and the most recent 2020 ML5.5 Zagreb and 2020 ML6.2 Petrinja earthquakes, point to the influence of local site effects. There is a reasonable indication that these earthquakes involved several localized site effects that could explain the increased intensity of half a degree or even up to one degree at certain localities compared to macroseismic modeling for rock condition. To better understand the influence of local site effects in the Međimurje region, the single-station microtremor Horizontal-to-Vertical Spectral Ratio (HVSR) method for subsurface characterization was used. Based on individual measurements, microzonation maps were derived for the Međimurje region to better understand the behavior of ground motion and the influence of local site conditions in comparison to macroseismic intensities and past damage observations. Several local site effects could be interpreted as a main contribution to site amplification and resonance effects due to variations in deep soft-deposit thicknesses overlayed on hard deposits and directional variations in topographical areas that could localize earthquake damage patterns. Correlations of microtremor analysis with intensity observations from historical earthquakes as well with recent earthquakes could help to distinguish local site zones prone to the possible occurrence of higher earthquake damage from nearby and distant earthquakes.

VIBRATION FORECAST IN EUROPE FROM THE RESULTS OF GROUNDWATER MONITORING ON THE TERRITORY OF UKRAINE

The article provides theoretical and practical arguments regarding the possibility of predicting local and strong distant earthquakes around the world, based on the detection of anomalous behavior of the groundwater physical properties in the Earth's tectonically stressed zones before local and strong earthquakes. The authors suggest that many strong and major events can be predicted at least a few months before they occur. The theoretical positions of the authors are confirmed by the successful prediction of an earthquake that occurred in Ukraine on January 21, 2022.

Seismic zoning maps of the National Capital Region (NCR) of India

AbstractWe present seismic zoning maps of the National Capital Region (NCR) of India in terms of uniform hazard spectrum (UHS) amplitudes using three different attenuation equations to model the contributions of local earthquakes around the region and distant earthquakes in northwestern Himalaya (NWH) and Hindu Kush Subduction (HKS) sources. Our results show that the shape of design spectra must depend on the nature of contributing earthquake sources, their relative activity, the potential to create large magnitudes, and their geographical placement relative to the site selected for hazard computation. Our results also show that specifying strong motion amplitudes for use in engineering design by means of peak ground acceleration and a standard spectral shape may result in significant underestimation of intermediate and long‐period ground motions critical for buildings higher than four to five stories and hence should not be used. We present zoning maps for nine possible combinations of three different local geological site conditions (sediments, intermediate sites, and basement rock sites) and three different soil site conditions (“rock,” stiff soil sites, and deep soil sites). One of these maps can be readily used to extract the UHS amplitudes of the pseudo relative velocity spectrum (PSV) at any site in the NCR by specifying the local geological site‐condition parameters from a high‐resolution surface geological map of the region and determining the local soil site conditions by experiments limited to the site alone. The paper also provides a geological map of NCR on a scale of 1:1 million for a rough idea of the local geological parameters for a site of interest.

Temporal changes of seismicity in Salton Sea Geothermal Field due to distant earthquakes and geothermal productions

SUMMARY The Salton Sea Geothermal Field (SSGF) is one of the most seismically active and geothermally productive fields in California. Here we present a detailed analysis of short-term seismicity change in SSGF from 2008 to 2013 during and right following large distant earthquakes, as well as long-term seismicity change due to geothermal productions. We first apply a GPU-based waveform matched-filter technique (WMFT) to the continuous data recorded by the Calenergy Borehole (EN) Network and detect more than 70 000 new micro-earthquakes than listed in the standard Southern California Seismic Network catalogue. We then analyse the seismicity rate changes in the SSGF associated with transient stress fluctuations triggered by regional and large teleseismic earthquakes from 1999 to 2019. We find triggered seismicity in the SSGF following seven regional M > 5.5 earthquakes. In comparison, most teleseismic earthquakes with M > 8.0 did not trigger significant seismicity rate change in the SSGF, likely indicating a frequency dependence in remote dynamic triggering. We further characterize the correlation between the long-term seismicity rate and geothermal production rates, and the temporal and spatial distribution of Guttenberg–Richter b-values inside and outside the SSGF with the newly detected catalogue. The long-term seismicity shows that events with M > 1.5 are likely correlated with net production rates, while smaller events do not show any correlation. The b-values inside the SSGF are higher than those outside the SSGF, and the locations of dynamically triggered events are close to locations with high b-values.

Surface-wave tomography using SeisLib: a Python package for multiscale seismic imaging

Summary To improve our understanding of the Earth’s interior, seismologists often have to deal with enormous amounts of data, requiring automatic tools for their analyses. It is the purpose of this study to present SeisLib, an open-source Python package for multiscale seismic imaging. At present, SeisLib includes routines for carrying out surface-wave tomography tasks based on seismic ambient noise and teleseismic earthquakes. We illustrate here these functionalities, both from the theoretical and algorithmic point of view and by application of our library to seismic data from North America. We first show how SeisLib retrieves surface-wave phase velocities from the ambient noise recorded at pairs of receivers, based on the zero crossings of their normalized cross-spectrum. We then present our implementation of the two-station method, to measure phase velocities from pairs of receivers approximately lying on the same great-circle path as the epicentre of distant earthquakes. We apply these methods to calculate dispersion curves across the conterminous United States, using continuous seismograms from the transportable component of USArray and earthquake recordings from the permanent networks. Overall, we measure 144 272 ambient-noise and 2055 earthquake-based dispersion curves, that we invert for Rayleigh-wave phase-velocity maps. To map the lateral variations in surface-wave velocity, SeisLib exploits a least-squares inversion algorithm based on ray theory. Our implementation supports both equal-area and adaptive parametrizations, with the latter allowing for a finer resolution in the areas characterized by high density of measurements. In the broad period range 4–100 s, the retrieved velocity maps of North America are highly correlated (on average, 96 per cent) and present very small average differences (0.14 ± 0.1 per cent) with those reported in the literature. This points to the robustness of our algorithms. We also produce a global phase-velocity map at the period of 40 s, combining our dispersion measurements with those collected at global scale in previous studies. This allows us to demonstrate the reliability and optimized computational speed of SeisLib, even in presence of very large seismic inverse problems and strong variability in the data coverage. The last part of the manuscript deals with the attenuation of Rayleigh waves, which can be estimated through SeisLib based on the seismic ambient noise recorded at dense arrays of receivers. We apply our algorithm to produce an attenuation map of the United States at the period of 4 s, which we find consistent with the relevant literature.