Swarm Events Research Articles

The landform Deformation at the Iraq-Iran Border due to Earthquakes in the Period (2017-2018)

The study targets to assess the potential of Interferometric Synthetic Aperture Radar (InSAR) in detecting ground distortion caused by earthquakes. The inSAR technique integrates Synthetic Aperture Radar (SAR) and interferometry to reveal the slightest changes on the earth's surface through a specified period, impregnable to climate or time of day. The research analyses some scholarly articles to demonstrate the interest of InSAR in examining earthquakes and their outcome. These articles demonstrate the practical application of InSAR in enhancing fault slip analysis, ground deformation assessment, and early post-seismic changes in earthquakes. InSAR is beneficial with measurements from other tools, such as GPS and time series analysis, but it still offers valuable insights into earthquake characteristics and associated effects. The insights from these methodologies can help devise solutions to mitigate the impacts of earthquakes. In addition, the paper presents information about three earthquake swarm events and their corresponding fault types. The first event occurred on November 12th, 2017, while the second happened on November 25th, 2018. Despite their differences in magnitude and location, the second event was associated with a strike-slip fault. InSAR provides extensive practical applications, from natural hazard monitoring to infrastructure projects and topographic mapping.

Historical earthquakes in the Holy Cross Mountains, Poland, true or false? Unveiling insights through archaeoseismology

The Holy Cross Mountains are an intraplate range with a limited historical seismicity record. The only documented earthquakes include the February 6, 1837 M 4.3 event, which caused ground cracks, and swarm events from February 1932 (M ∼ 3.5), likely triggered by the Holy Cross Fault (HCF) or sub-perpendicular faults. The apparent lack of older destructive earthquakes in historical catalogs motivated us to conduct archaeoseismological research to improve seismic hazard assessment, risk mitigation, and urban planning strategies, ultimately benefiting local communities. We focused on the 12th-century Collegiate church of Saint Martin in Opatów, located near the Holly Cross Fault (HCF). We report numerous damage features, such as leaning, bulging, and twisted walls, dropped keystones in Romanesque and Gothic portals, strike-slip displacements of these portals, surplus, oversized buttresses, and walled-up portals. While some deformations may result from humid loess instability and war destructions, our data, combined with historical records, suggest two to three seismic events in the past 800 years as a cause. We argue these deformations were co-seismically triggered by either large far-field events, like the 1259 AD earthquake, or local, shallow small-magnitude events significantly amplified by site effects. This indicates potential seismic activity in the Holy Cross Mountains during Medieval times. The absence of historical records does not imply the absence of earthquakes.

A newly recognised mafic sill-hosted Ni-sulfide deposit emplaced during the 2.4 Ga Widgiemooltha dike swarm event, Eastern Goldfields, Western Australia

AbstractThe Cathedrals Ni-Cu prospect, located at the western margin of the Eastern Goldfields of the Yilgarn Craton, is hosted within a mafic intrusion interpreted as a sill complex. U-Pb dating of apatite from the sill yielded a crystallisation age of 2336 ± 64 Ma, inferring an association of sill emplacement and Ni mineralisation related to emplacement of the c. 2400 Ma Widgiemooltha dike swarm. The sill is typically differentiated into a lower olivine orthocumulate layer overlain by a dolerite unit containing xenoliths of partially assimilated granitoids in its upper portion. The latter is interpreted to be the result of stoping and melting of the granitic hanging wall, thereby creating a gravitationally stable buoyant melt layer beneath the top contact. Ni-Cu-Fe sulfides are increasingly abundant towards the base of the sill, ranging from globular disseminated sulfides to net-textured and massive sulfides at the basal contact. The presence and orientation of sulfide globule-bubble pairs indicates a primary near-horizontal orientation. Massive sulfides commonly exhibit a loop texture with pyrrhotite grains surrounded by pentlandite and chalcopyrite. Despite the variety of sulfide textures, sulfur isotopes have a homogeneous mantle-like signature without significant mass independent fractionation. Mineral chemistries that indicate sulfide prospectivity in larger intrusions do not work as effectively in this small sill, therefore new indicators may need to be developed to explore for similar deposits. To date, there are no other known magmatic deposits of this age in Australia. Sills of this age may be more prospective than previously recognised.

Statistical Analysis of Mt. Vesuvius Earthquakes Highlights Pitfalls in Magnitude Estimation

Here, we characterize the statistical behaviour of the Mt. Vesuvius seismicity using distinct available catalogues. Our analysis confirms that for this area, the GR distribution exhibited two scaling regimes of the b-value, not commonly observed for the standard frequency-magnitude distribution of earthquakes. By assuming a physical cause, we tested four different hypotheses for the source of the break in the scaling: finite size effect, depth variations in the b-value, radial dependence in the b-value, and different b-values for swarm and non-swarm events. None of the above reasons are able to explain the observation. Thus, we investigated the possibility of some pitfalls in magnitude estimation. Based on our analysis, we suggest there is a bias in the duration magnitude the catalogues are based on. This is due to the arbitrary extrapolation to smaller magnitudes of a linear regression derived for earthquakes with m≥3.0. When a suitable correction is applied to the estimated magnitude, the GR distribution assumes the usual shape, with a b-value closer to that usually observed in volcanic areas. Finally, the analysis of the time variation of some statistical parameters reveals that the state of the volcano appears to be stationary over the entire analysed period, possibly with only a slight decrease in the b-value, indicating a small reduction in differential stress.

Updip Fluid Flow in the Crust of the Northeastern Noto Peninsula, Japan, Triggered the 2023 Mw 6.2 Suzu Earthquake During Swarm Activity

AbstractAn Mw 6.2 earthquake occurred in Suzu, northeastern Noto Peninsula, Japan, on 5 May 2023, followed by many aftershocks. Before this mainshock‐aftershock sequence, an intense earthquake swarm lasted in the vicinity for 2.5 years. Here, we estimated the rupture process of the Mw 6.2 mainshock and relocated >20,000 surrounding small earthquakes. The results show that systematic upward migration occurred via a complex network of faults in the preceding swarm period and that the mainshock rupture was initiated near the shallow end of the swarm earthquakes. The mainshock rupture propagated farther updip, followed by many aftershocks in the shallow extension. Upward fluid movement likely caused systematic upward earthquake migration from a depth of 18–5 km. The present results indicate the importance of monitoring swarm events since large (M > 6) and dangerous earthquakes can occur during such swarms.

Detection and Characterization of Earthquake Swarms in Nankai and Its Association With Slow Slip Events

AbstractVarious types of slow earthquakes occur in the Nankai subduction zone, among which the slow slip events (SSEs) seem to connect the shallow and deep part of the subduction plate and further trigger seismic or aseismic transients in surrounding areas. This study uses a version of space‐time epidemic‐type aftershock sequence (ETAS) model with non‐stationary background rate to detect earthquake swarms that may be related to SSEs in the Nankai region. We detect 999 swarm sequences including 13,387 earthquakes, accounting for about 18 percent of all M ≥ 1.0 earthquakes in the selected region along the Nankai trough. The detected swarms are mostly distributed in the Hyuga‐nada, Bungo Channel, Kii Channel, and Tokai regions, forming a complementary pattern to SSEs. Nearly 70 percent of swarm events are located in western Nankai, with the southern part characterized by a higher occurrence rate, which is consistent with the smaller recurrence interval of SSEs in this region. By comparing occurrence times of swarm events to those of SSEs, we find that some SSEs are accompanied by enhanced swarm activities during their occurrence periods. In addition, the swarm rates increase to higher levels in the southern part of western Nankai during the 2003 and 2010 Bungo SSEs, indicating the high sensitivity of earthquake swarms to the migrations of slow earthquakes in this region.

High Activity Earthquake Swarm Event Monitoring and Impact Analysis on Underground High Energy Physics Research Facilities

A seismic swarm is a series of earthquakes that occur in a small area over a short period of time. A sequence of earthquakes of this magnitude is unusual in Switzerland, and it is impossible to anticipate how it may unfold in the future.The seismic activity of such an event usually fades after a few days or weeks. Significantly greater earthquakes are likely to occur during the next several days, with up to a chance of 5 to 10%. For these reasons, the underground research facilities need tools to provide data on the impact of these events on their experiments. The paper presents the techniques implemented at The European Organization for Nuclear Research (CERN) to allow the tracking and monitoring of these unusual events. Additionally, the real effect of such an unusual event is presented together with the statistical approach to monitoring and effect evaluation. Considering the collision energy of the beams at 14 TeV, the energy stored in the magnets at 10 GJ (2400 kg of TNT), and the energy carried by the two beams at 724 MJ (173 kg of TNT), prolonged exposure to vibration close to or above the set alarm levels may result in serious safety issues. The presented evaluation of earthquake swarm impact on underground facilities together with the approach for data evaluation can be used for the design of future detectors and accelerators. Additionally, it provides tools for facilities users to present the data in an easy to understand way. This includes the Future Circular Collider, whose purpose is to significantly expand the energy and intensity frontiers of planned particle colliders, with the goal of reaching collision energies of 100 TeV in the quest for novel physics. As a result, even greater standards for beam size and stability will be required.

Detection of Aseismic Slip and Poroelastic Reservoir Deformation at the North Brawley Geothermal Field From 2009 to 2019

AbstractThe North Brawley Geothermal Field, located within the Brawley Seismic Zone of Southern California, presents a case study for understanding seismic hazards linked to fluid injection and geothermal energy extraction. An earthquake swarm near the geothermal field in 2012 included two earthquakes with magnitudes greater than 5 and was potentially preceded by a years‐long aseismic slip transient. To better understand ground deformation around the geothermal field, including its evolution with time and its physical mechanisms, we analyze deformation before, during, and after the swarm using ground‐ and satellite‐based geodetic techniques between 2009 and 2019. We integrate observations from GNSS, Sentinel‐1, TerraSAR‐X, UAVSAR, and leveling surveys into a single deformation history. Modeling of this new collection of observations at the North Brawley Geothermal Field provides evidence for 80% more pre‐swarm aseismic slip than previously recognized from 2009 to 2012. During the 2012 Brawley swarm, our geodetic slip inversions closely match the results of seismic waveform inversions from the swarm events. After the 2012 swarm, surface deformation is dominated by poroelastic deformation of a shallow fluid reservoir at <1 km depth rather than fault slip. The deformation history and seismicity catalogs at North Brawley suggest a cessation of fault‐related slip during the ∼7 years after the 2012 earthquake swarm.

Numerical Study on the Characteristics of AbyssalT-Wave Envelopes Controlled by Earthquake Source Parameters

AbstractHydroacoustics has been successfully applied to detect and locate small-to-intermediate submarine tectonic activities infrequently recorded in land-based seismic arrays. However, to extend the utilization of T waves to extract other important earthquake source parameters, such as source strength, the roles of earthquake focal mechanisms, and source depths in T-wave envelopes must be thoroughly understood. We performed 3D numerical modeling considering anisotropic source radiation and realistic scattering in the oceanic crust for two focal mechanisms (normal and strike-slip faults) and three depths (5, 10, and 15 km) to investigate the effect of source radiation and focal depth on abyssal T waves. By analyzing the synthetic T-wave envelopes, we showed that stronger SV-energy radiation from a normal-fault earthquake event generates higher-intensity T waves of the same source magnitude. The anisotropic source radiation of a double-couple source causes azimuthal changes in the shapes of T waves, and deeper earthquakes cause gentle-sloped envelopes; however, the slopes also vary with respect to the azimuths of receivers and focal mechanisms. Temporal changes in the slopes of T-wave envelopes of magmatic swarm events near Wordie Volcano, Bransfield Strait, Antarctic Peninsula, imply that the depth dependency can be utilized to determine relative depths for hydrothermal-vent events or sequenced earthquakes.

Earthquake Swarm Analysis around Mt. Salak, West Java, Indonesia, Using BMKG Data from August 10 to November 24, 2019

Earthquake swarms commonly come approximately active tectonic and volcanic area. Interestingly, the swarm events occurred ~23 km southwest from Mt. Salak-Bogor, West Java, Indonesia, from August 10 to November 24, 2019, and were recorded by local/regional network of the Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG). Our previous study showed that in this area a destructive ML 4.6 earthquake with thrust faulting occurred on September 8, 2012. The double-difference method was applied to update the hypocenter locations from the BMKG data. In the time period of ~3.5 months, we relocated 79 swarm events with ~9.4 km depth average for local magnitude (ML) 2.2 to 4.2. The source mechanism result for selected events shows a strike-slip faulting. Our interpretation is that these swarm events are probably related to stress change due to volcano-tectonic activity.

Earthquake swarms in Taiwan: A composite declustering method for detection and their spatial characteristics

Earthquake swarms can act as indicators of fluid activity and aseismic transients at depth. As a young and active collisional mountain belt with frequent earthquakes, Taiwan is a natural laboratory for studying the physical mechanisms controlling the characteristics of swarm activity in this complex tectonic environment. Where the earthquake swarms tend to occur and how they reflect the aseismic deformation in this young orogen? In this study, we propose a composite swarm detection method that relies on the correlation of mainshock density rates derived from three distinct declustering algorithms. Using earthquakes in Taiwan from 1990–2019 with magnitudes greater than or equal to three and at depths less than 50 km, 153 swarm sequences were identified as characterized by an event number greater than ten, a time span of less than fifteen days, and a maximum magnitude of 5.79. The swarm sequences were found to be active at locations with a high seismicity rate (>0.2yr−1km−2) but not an anomalous b-value, suggesting that the environment with a high rate of earthquake occurrence is linked with the mechanism for swarm generation. They were found to largely overlap with the repeating earthquakes, as approximately 86% of the 1857 repeating events in Taiwan are closely located to swarm events. Such overlap is found to be largest in the southern Longitudinal Valley where a creeping fault is located and where a low coupling ratio was inferred. Consequently, it is proposed that the active collision boundary experiencing a high creep rate and the areas experiencing episodic aseismic slip are capable of producing active swarm sequences in Taiwan.

Source Parameters of Microseismic Swarm Events Induced by the Explosion at the Korobkovskoe Iron Ore Deposit

Source Parameters of Microseismic Swarm Events Induced by the Explosion at the Korobkovskoe Iron Ore Deposit

Initiation of continental breakup documented in evolution of the magma plumbing system of the ca. 925 Ma Dashigou large igneous province, North China

In the Wilson cycle, continental rifting leads to ocean basin formation, but the relationship between rift-related magmatism and the initiation of seafloor spreading and continental drift remains unclear. A recently recognized large igneous province (LIP), the ca.925 Ma Dashigou LIP of the North China Craton, possibly represents initial of continental breakup. The magmatic center of this LIP is thought to be located in the Xuhuai basin, where two generations of sill complexes (945–920 Ma Niutishan and 915–890 Ma Pingshan) occur. Both complexes are dominantly tholeiitic, with minor alkaline rocks in the Pingshan complex. The Niutishan complex compositionally varies from gabbro (SiO2 = 48.0–49.0 wt%, MgO = 4.0–6.0 wt%) to quartz dolerite (SiO2 = 53.0–56.0 wt%, MgO = 2.0–3.0 wt%), while the Pingshan complex is comprised of more primitive gabbro (SiO2 = 47.0–48.5 wt%, MgO > 6.0 wt%) with only a few quartz syenite veins (SiO2 = 58.5–59.8 wt%, MgO = 1.0–1.2 wt%). Trace elements and isotopic compositions indicate a relatively minor continental signature in the Niutishan parental magma (87Sr/86Srinitial = 0.7040–0.7048, εNdinitial = −0.84 to +1.91, Nb/La = 0.8–1.2), while Pingshan exhibits transitional to MORB compositions and shows distinct geochemical signals of seawater alteration (87Sr/86Srinitial = 0.7060–0.7079, εNdinitial = −1.34 to −0.23, Nb/La = 0.6–0.7). The compositional ranges of both units are consistent with varied degrees of partial melting in the source regions followed by varied degrees of fractionation in the magma chambers/plumbing systems. Sr isotopic characteristics indicate a possible increasing in alteration of oceanic fluids through time. Coherent geochemical features show that the far-field radiating Dashigou dyke swarm and Niutishan events belong to the plumbing system of a single LIP in a pre-drift environment. The Pingshan complex is probably related to the growth of an inner subaerial seaward-dipping syn-rift reflector sequence. The plumbing system evolved from a sill complex (Niutishan) near the magmatic center at ca. 945 Ma to a far-field radiating dyke swarm (Dashigou) at ca. 925 Ma, which then reverted back to a sill complex (Pingshan) near the magmatic center at ca. 915 Ma. The Dashigou LIP may be correlated with the Bahia-Gangila LIP of the São Francisco-Congo Craton, and the evolution of their magmatic plumbing systems is interpreted as an indication of rift-to-drift transition tectonics, which resulted in the initiation of seafloor spreading and consequent drift.

Source and path effects of the ground motions recorded during the 2020 Haenam earthquake swarm in South Korea

On the southwestern Korean Peninsula, a 74-earthquake swarm was recorded between April 26 and May 9, 2020, with a maximum local magnitude (ML) of 3.1. This is the third such event since instrumental seismic recordings began in South Korea in 1978. Because this area is located on a stable continent, this rare swarm event provides an opportunity to analyze earthquake sources and attenuation characteristics in this region. In this study, we first analyzed the intensity measure (IM) and the frequency content of the ground motions recorded during this swarm event. Next, we investigated the effects of earthquake magnitude and source-to-site distance on IMs, compared with those derived from international and local ground-motion models (GMMs). We found that the magnitude scaling slope (i.e., variation of IMs depending on ML) of the earthquake swarm records for ML ≥ 1.8 is similar to the slopes derived from GMMs, while for ML < 1.8, the slope from the records is steeper. For distance scaling (i.e., variation of IMs depending on source-to-site distance), the slopes from records are gentler than those from GMMs. This indicates that ground motion attenuates slowly in this region, compared to other global regions.

Study of P and S Wave Quality Factor (Qα and Qβ) Around Mt. Jailolo

Mt. Jailolo is a B type volcano that has never erupted after 1600. Seismic activities around Mt. Jailolo have never been recorded until the swarm in November 2015. Several studies have been done to determine thecause of the swarm, but it is not certain whether the cause of the swarm is tectonic or volcanic activities. The study of attenuation characteristics has never been carried out in the area around Mt. Jailolo. Attenuation characteristics are important to provide the medium information which seismic waves pass through and it can also be applied to the volcanic areas as preliminary disaster mitigation. The main objective of this study is to analyze attenuation characteristics often expressed by Quality factor (Q-factor) of P and S seismic wave (Qα and Qβ), which are inversely proportional to attenuation factor (1/Q). Calculations of Qα and Qβ are obtained using coda normalization method. The study area location is around Mt. Jailolo at 127.3◦ - 127.6◦E and 0.9◦ - 1.2◦ N. Data have been collected with 12 Short Period temporary 7G sensors network belongs to GFZ and BMKG. This study uses 147 swarm events from the sensors with a threshold magnitude of Mw&lt; 5.0, during April 2017. The study obtains Qα(f) = 9.61814f 1.12981 and Qβ(f) = 19.10690f 1.22843. The current analysis concludes that the attenuation beneath Mt. Jailolo corresponds to the volcanic swarms which may have been triggered by its deeper layer’s magmatic activity.

SH-waveform modeling of small local seismic events in Ladoga lake

A lot of seismic phenomena with small magnitude has been taking place in the Ladoga lake region (northwestern Russia). One of them is the earthquake which was recorded on the 31st of July, 2010 followed by the swarm of microearthquakes near Nikonovsky cape. There is only one station in the region that is why it is difficult to process the data. In this work, we propose a new approach to construct synthetic seismograms of the main event with minimum data. Also this approach applies us to calculate parameters of the source. The approximate magnitude of the main event is $$M_L=-0.8$$ . For swarm events, we have magnitude values from $$-\,1.0$$ to $$-\,2.6$$ . The data of swarm events (microearthquakes) is used to test the technique of constructing synthetic seismograms. The approach we propose is based on Green’s function method with using two temporal $$\delta$$ -sequences (the Lorentzian function and the continuous Dirichlet kernel). A comparison of synthetic and real seismograms shows that the Lorentzian function is better to describe small local events, and the continuous Dirichlet kernel is more appropriate for earthquakes. This approach can be generalized to various problems of different nature.

Гагатлинский рой слабых землетрясений – проявление активности Андийского разлома

The swarm of more than a hundred weak earthquakes, the bulk of which occurred in the second decade of January 2019, was recorded at the end of 2018 and at the beginning of 2019 in the area of the western borders of the Dagestan salient. Refinement of the position of the epicenters of the swarm events by the method of double differences showed their compact location to the northeast of the village Gagatli on the eastern latitudinal branch of the Andean fault, known for left-lateral strike-slip and normal fault kinematics. According to the results of the study of the fault plane solutions of the five most strong earthquakes in the swarm, the type of movement was established - a left-lateral strike-slip and normal component, which allowed the investigated activation to be attributed to the discharge of accumulated stresses in the eastern part of the Andean fault. A characteristic feature of the recordings of these events by the nearest stations located in the territory of Dagestan and Chechnya was the similarity of the wave pattern, established when they correlated in different frequency bands (1-2 Hz, 1-3 Hz, 1-5 Hz). The correlation matrix of the records of 19 events filtered in the 1-3 Hz band was used to construct cluster analysis dendrograms showing different correlation of the events of the swarm and other earthquakes of Dagestan at a similar distance.

Multipoint Field‐Aligned Current Estimates With Swarm

AbstractField‐aligned currents (FACs) are a key component of the magnetosphere‐ionosphere system, providing the transfer of energy and momentum between the distant collision‐free magnetospheric plasma and the collisional ionosphere. The European Space Agency's Swarm mission offers a unique opportunity to explore the FACs low‐altitude end by a broad range of single‐spacecraft and multispacecraft techniques. The present technical report demonstrates the application of dual‐ and three‐satellite FAC estimation methods based on the least squares approach, with the goal to enhance the use of Swarm data in exploring the high‐latitude current structures, beyond the official FAC product presently available to the end user. The dual‐satellite method presents some clear advantages since it provides stabler solutions, can be applied on a more general spacecraft configuration, and offers a robust error estimation scheme. Consequently, the method provides significantly more data near the singularity where the satellites' orbits intersect, allows FAC estimation with configurations that involves the upper Swarm satellite, or to fine tune the constellation geometry to the problem at hand. Similarly, the three‐satellite method, meant to be applied when Swarm forms a close configuration, brings additional valuable information, associated to a different (larger) scale. Moreover, it can estimate the FAC density with high time resolution when instantaneous measurements are used. The performance of the methods are thoroughly analyzed both on Swarm events and on simulated data, and the results are compared with other available methods. Particular emphasis is put on how different FAC estimation methods complement each other and provide consistent results.

A standardised protocol for the evaluation of small extracellular vesicles in plasma by imaging flow cytometry

Flow cytometry provides robust, multi-parametric and quantitative information on single cells which also exhibits enormous potential as a tool for small particle characterisation. Small extracellular vesicle (sEV) detection by flow cytometry remains compromised due to the high prevalence of swarm detection, which is defined by the simultaneous illumination of more than one sEV, recorded as a single event. Detection of sEVs by imaging flow cytometry presents a major advantage by having the ability to resolve single particles from swarm detection based on the image features recorded for each event. In this study, we provide a simplified protocol that facilitates the removal of both swarm events and aggregated particles to improve the accuracy of sEV analysis. Our results indicate that imaging flow cytometry should be at the forefront as a robust and sensitive technique for sEV characterisation.

Variations in Cascadia Low‐Frequency Earthquake Behavior With Downdip Distance

AbstractWe identify and characterize four different low‐frequency earthquake (LFE) families (LFEs 1–4, ordered updip to downdip) that span the width of the transition zone in the Cascadia Subduction Zone beneath western Washington State. We find that LFE swarm duration, recurrence interval, and event size decrease systematically with increasing depth. LFE moments are observed to follow an exponential distribution rather than a power law distribution, allowing us to determine a characteristic event size for each family. Absolute locations of these LFE families place them very near the inferred Juan de Fuca‐North America plate interface. Relative relocation of individual LFEs within each family reveal elongation parallel to the plate convergence direction and narrow depth distributions with dips corresponding to plate interface models. We interpret the behavior of our LFE families as indicative of slow slip at those locations on the plate interface. The tidal response of LFE activity at LFEs 1, 2, and 3 during a large episodic tremor and slip (ETS) event follows a previously observed evolution, in which tidal response during the initial 1 to 2 days of slip at an LFE patch is much weaker than that during the next few days of slip. The brief bursts of activity at LFE4, although little affected by large episodic tremor and slip events, respond strongly to tidal stresses. Our observed along‐dip contrasts in recurrence behavior and tidal response provide evidence for stress transfer and increased frictional strength with position updip through the tremor zone.