Explosive Events Research Articles

Experimental and simulation studies on suppressing gas explosions with diverse atomized liquid droplets: Insights for improved safety in mining

Gas explosions represent a prevalent thermodynamic hazard in coal mining, significantly endangering worker safety and the operation's overall safety. Water mist stands out among various explosion suppression techniques due to its high heat absorption capacity and environmental sustainability, offering a promising avenue for application. This study introduces a custom-built pipeline gas explosion testing apparatus to investigate the suppression effects of different atomized liquid droplets on gas explosions. By collecting and analyzing experimental data from pressure sensors under varying conditions within the pipeline, we conduct a thorough comparison of the explosion suppression characteristics attributed to different atomized droplets. Based on this foundation, the Fluent software was used for numerical simulation research to further analyze the explosion suppression effects of different atomized droplets. Additionally, numerical simulations were conducted to optimize the nozzle arrangement. Our findings reveal that an increase in atomization pressure, leading to smaller droplet sizes, significantly mitigates the impulse of the gas explosion shock wave. This indicates a marked inhibitory effect of atomized droplets on gas explosions, with finer droplets showing enhanced suppression capabilities. The simulation results from the optimized nozzle arrangement can provide valuable guidance for on-site deployment. Through a combination of experimental and simulation data, this study conducts a qualitative and quantitative analysis of the suppression mechanisms offered by different atomized droplets, considering parameters such as explosion impulse, blast energy, and explosion indices. The insights gained provide a theoretical foundation for reducing the ring-breaking effect of gas explosions and enhancing explosion suppression strategies, which are crucial for ensuring the safety of coal mining operations.

Insights into the Fragmentation of Aluminum Hydride and Its Effect on Combustion and Agglomeration of HTPB Propellant.

AlH3 has gained considerable attention as a fuel additive due to its ability to offer high specific impulse and superior combustion performance. However, few studies have focused on the fragmentation and agglomeration behavior of AlH3. This study investigated the effects of fragmentation of AlH3 and AlH3/PVDF particles on the thermal decomposition, ignition, agglomeration, and combustion of HTPB propellants. Thermal analysis indicated that AlH3 and AlH3/PVDF can accelerate the decomposition of ammonium perchlorate by abundant active sites for the adsorption of the decomposition intermediates. Single-particle combustion uncovered the mechanism behind the directional spray of molten Al from the AlH3 particle and the fragmentation of the AlH3/PVDF particle. The melting of porous Al induces particle shrinkage due to solid-liquid interfacial tension and the structural restoration of the oxide shell, which consequently results in the sealing of cracks in the oxide shell of AlH3. Additionally, the accumulation of internal tensile stress leads to the reopening of these cracks and the directional ejection of the molten Al. The flexible oxide shell contributes to a smaller minimum normalized diameter of the AlH3/PVDF particle, aiding in the generation of internal tensile stress, while the sublimation of AlF3 induced the fragmentation. Synchrotron-based X-ray imaging revealed the formation of aggregates promoted by molten Al, the splitting of AlH3 aggregates due to hydrogen explosion, and the enhanced fragmentation of AlH3/PVDF due to the synergistic effect of hydrogen explosion and the sublimation of AlF3. Compared to raw particles, the CCPs (condensed combustion products) of SP2 propellant display a 48% reduction in average size (D50 = 24.5 μm), whereas there is an over 89% decrease in particle size for the CCPs of SP3 propellant (D50 = 5.14 μm). This study contributes to understanding the fragmentation of AlH3 and AlH3/PVDF upon ignition and combustion, providing valuable insights for the development and optimization of propellants containing AlH3.

Weather radar utility in hazard detection and response.

Publicly accessible weather radar data have significant capabilities for meteorological measurements and predictions and, further, have the potential to measure nonmeteorological events that include smoke, ash, and debris plumes as well as explosions. The ability to identify and track nonmeteorological events can be of assistance in emergency response, hazard mitigation, and related activities in locations where radar coverage both exists and is recorded and accessible to the user. In this study, events from multiple locations in the United States that are reported in news outlets are assessed using a manual inspection process of Level 2 weather radar data to identify anthropogenic and nonbiological returns. Explosive events are also identified, and a large high-altitude debris cloud from the intentional destruction of the SpaceX Starship is tracked across a wide area. Finally, future efforts using a machine learning model are discussed as a means of automating the process and potentially enabling near-real-time nonmeteorological event identification in the same areas where the data are accessible. Using weather radar data can be a valuable new tool for Department of Defense systems to aid in military awareness, and for interagency emergency response and forensic mission experts to consider national weather service data in their mission profiles. Radar data can be effective in detecting several common types of emergencies and inform and aid response personnel.

Investigation of hydrogen explosion effects based on cavity structure-porous material coupling

Porous materials have good wave-absorbing and shock-absorbing effects, so it is one of the common measures to adopt them for explosion isolation in the field of safe transportation of hydrogen energy, but the need for filling inside the pipeline limit its application. In this paper, based on the structure-material coupling mechanism, the porous material is placed in the vacuum cavity structure. The explosion-proof performance of the polyurethane(PU) filled with different pore sizes and the composite material is investigated, which provides theoretical support and experimental basis for the application of porous material in the field of the explosion-proof. It is found that the coupling mechanism of "vacuum cavity - porous material" can effectively reduce the explosion pressure in the pipeline, and the smaller the pore size of the porous material, the stronger the effect of explosion isolation, and the maximum reduction in explosion pressure of 74 %. On this basis, the shear thickening gel (STG) and PU composite, give it the performance of impact hardening, and improved mechanical properties, the experimental results show that the composite material after the explosion isolation performance is stronger, the maximum explosion pressure attenuation of 87 %, the explosion isolation performance increased by 18 %.

The sound of lichens: ultrasonic acoustic emissions during desiccation question cavitation events in the hyphae.

Lichens are a mutualistic symbiosis between a fungus and one or more photosynthetic partners. They are photosynthetically active during desiccation down to relative water contents (RWCs) as low as 30% (on dry mass). Experimental evidence suggests that during desiccation, the photobionts have a higher hydration level than the surrounding fungal pseudo-tissues. Explosive cavitation events in the hyphae might cause water movements towards the photobionts. This hypothesis was tested in two foliose lichens by measurements of ultrasonic acoustic emissions (UAEs), a method commonly used in vascular plants but never in lichens, and by measurements of PSII efficiency, water potential, and RWC. Thallus structural changes were characterized by low-temperature scanning electron microscopy. The thalli were silent between 380% and 30% RWCs, when explosive cavitation events should cause movements of liquid water. Nevertheless, the thalli emitted UAEs at ~5% RWC. Accordingly, the medullary hyphae were partially shrunken at ~15% RWC, whereas they were completely shrunken at <5% RWC. These results do not support the hypothesis of hyphal cavitation and suggest that the UAEs originate from structural changes at hyphal level. The shrinking of hyphae is proposed as an adaptation to avoid cell damage at very low RWCs.

Hard X-rays from the deep solar atmosphere: An unusual UV burst with flare properties

Explosive transient events occur throughout the solar atmosphere. The differing manifestations range from coronal mass ejections to Ellermann bombs. The former may have negligible signatures in the lower atmosphere, and the latter may have negligible nonthermal emissions such as hard X-radiation. A solar flare generally involves a broad range of emission signatures. Using a suite of four space-borne telescopes, we report a solar event that combines aspects of simple UV bursts and hard X-ray emitting flares at the same time. The event is a compact C-class flare in active region AR11861, SOL2013-10-12T00:30. By fitting a combined isothermal and nonthermal model to the hard X-ray spectrum, we inferred plasma temperatures in excess of 15\,MK and a nonthermal power of about $3 xii and xxi emission lines, which are characteristic of emission from hotter plasma with a temperature over 1\,MK. Moreover, the event exhibited very limited signatures in the extreme-UV wavelengths. Our study indicates that a UV burst -- hard X-ray flare hybrid phenomenon exists in the low solar atmosphere. Plasma that heats to high temperatures coupled with particle acceleration by magnetic energy that is released directly in the lower atmosphere sheds light on the nature of active region core heating and on inferences of flare signatures.

Study of damage mechanism on single crystal 4H-SiC surface layer by picosecond laser modification (PLM)

The stable structure, high hardness, and brittleness of single-crystal 4H-SiC present challenges in achieving efficient and damage-free polishing processing. Ultra-short pulsed laser-induced surface modification provides a new solution to enhance the manufacturability of 4H-SiC. This paper aims to investigate the underlying mechanism of the picosecond laser-induced surface structural changes in 4H-SiC and the process of material removal from solid to vapour, elucidating the interaction mechanism between picosecond laser and 4H-SiC. A temperature gradient distribution model for picosecond laser irradiation on 4H-SiC was built to reveal the formation mechanism of subsurface crack damage. The results show that a combination of phase explosion and thermal effects controlled picosecond laser-modified 4H-SiC surfaces deposited spherical SiO2 particles and the process. The study demonstrates that the cracking behaviour in the subsurface of picosecond laser-modified SiC predominantly occurs in the recast region. The fundamental cause of cracking is attributed to the tensile stresses generated by thermal effects and the volumetric changes in the molten material resulting from the overlapping of neighbouring spots in alternating hot–cold cycles. The nanoindentation demonstrated that laser modification can effectively enhance the machinability of SiC. The findings of this study can provide a theoretical basis for efficient non-destructive machining of hard and brittle materials.

Tungsten wall cratering under high-velocity dust impacts: Influence of impact angle and temperature

The integrity of plasma-facing components (PFCs) in fusion reactors is severely tested by high-velocity dust collisions, which occur during explosive events such as runaway electron terminations. These events can expel dust particles at velocities of 0.5 – 1 km/s in current fusion devices and potentially several km/s in advanced reactors like ITER and DEMO, leading to significant material erosion and damage. Given the limitations of existing models, which effectively address only low-velocity impacts, there is a critical need for improved modeling of high-velocity dust-wall interactions. This study utilizes molecular dynamics (MD) simulations to explore the effects of impact angle and target temperature on the interactions between tungsten (W) dust particles and W walls under extreme velocities ranging from 2.5 to 4.5 km/s. Our research focuses on analyzing the morphology of impact craters, and characteristics of ejecta across a range of impact angles (0° to 75°) and with dislocation density for temperatures (300 to 3000 K). Our study reveals that the angle of impact and temperature almost exclusively determine the shape of the crater and the distribution of ejecta, highlighting the critical role of these factors in the dynamics of dust-wall interactions. Comparison with the experimental data obtained from W-on-W impact tests shows a strong correlation with our theoretical predictions.

Ignition and combustion characteristics of magnesium-based nanofluid fuel

Mg-based nanofluid fuel is a promising fuel for propulsion system in Mars exploration. In this study, Mg-based nanofluid fuel were prepared by one-step method, and the effect of Mg(magnesium) content, Mg size(68 μm,110 μm,175 μm), and oleic acid (OA) on droplet ignition and combustion under the atmosphere of 90 % CO2 and 10 % O2 were investigated. According to the TG-DSC results, 68 m Mg particles under CO2 had the highest exothermic efficiency of 4472 J/g. The combustion of Mg/OA/kerosene droplets consists of five stages: ignition, d2-law combustion, micro-explosion, vapor flame extinguishment, and agglomerate explosion. The ignition delay time of Mg (68 μm, 5 %)/kerosene is 0.045s, which is half that of kerosene (0.0890s). The agglomerates explode violently and emit a brilliant white light at the end of the Mg-based nanofluid fuel combustion. The explosive effect of Mg agglomerates diminishes as the Mg content increases. The rate of combustion decreases with increasing particle size. In the sample with added oleic acid, Mg (68 μm, 5 %)/OA/kerosene shows the best combustion rate of 0.6320 mm2/s. Finally, a numerical model for the combustion of Mg-based nanofluid fuel droplets is proposed. The predictions are within 2 % of the experimental results. The findings are expected to explore future in-situ utilization of CO2 on the Mars surface.

Can the Phoenix still rise? Traumatic effect of Beirut port explosion on Lebanese people's experiences.

Mental distress and decreased functionality are highly prevalent after collective traumas. Survivors' ability to function is worsened by untreated distress and unmet needs related to job security and a sense of belonging. We aim to identify groups of people using a latent class analysis based on multiple dimensions of subjective experiences after a massive urban violent event. This cross-sectional internet-based study included 1,305 Lebanese adults 4 months after the Beirut Port explosion. Emotions, attitudes, and needs were assessed using the iCode software, a novel approach measuring explicit subjective answers and implicit reaction time to various statements. Responses revealed alarming levels of distress with 75%-80% of participants feeling anxious. Latent class analysis differentiated three groups on initial dimensions derived from the principal component analysis. The first group included those with the most intense emotional distress and intrusive thoughts. They were younger, had higher job worries, and wanted to leave the country. The second group was equally distressed, with marked intrusion and avoidance yet with faith and community resilience buffering negative emotionality. The last group was less distressed with a marked sense of community. Clustering people based on emotional experiences, needs, and resources might offer additional benefits to traditional assessments that fail to detect the variability of vulnerability to mass violence within seemingly homogeneous samples. Integrating implicit and explicit responses also helps with a rapid classification, providing insight to subjective attitudes postcollective trauma. The study mostly provides suggestions for targeted outreach to at-risk subpopulations to better foster resilience in unstable environments. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Determining the viewing angle from TeV light curve of GRB 221009A

ABSTRACT Gamma-ray bursts (GRBs) are among the most powerful explosive events in the Universe. LHAASO recently observed the most luminous one: GRB 221009A, and unveiled its TeV light curve. The light curve exhibits a distinct jet break at around 670 s, enabling the derivation of the viewing angle based on the smoothness of the jet break. We constructed two models with or without considering the high-latitude radiation, where the viewing angle was treated as a free parameter, to fit the TeV light curve. The viewing angles obtained were 9.4 $\times 10^{-4}$ and 5.9 $\times 10^{-3}$ rad, respectively. These values closely resemble an on-axis scenario, given the opening angle is 1.4 $\times 10^{-2}$ rad.

Steam Explosion Pretreatment of Polysaccharide from Hypsizygus marmoreus: Structure and Antioxidant Activity.

This paper investigated the effects of steam explosion (SE) pretreatment on the structural characteristics and antioxidant activity of Hypsizygus marmoreus polysaccharides (HPS). Hypsizygus marmoreus samples were pretreated at different SE temperatures (120-200 °C) and polysaccharides were extracted using the water extraction and alcohol precipitation method. The results showed that SE pretreatment improved the extraction rate of HPS. Under the conditions of SE treatment time of 60 s and temperature of 160 °C, the extraction rate of HPS was the highest (8.78 ± 0.24%). After SE pretreatment, the structural changes of HPS tended to enhance the antioxidant activity, which showed that the content of Gal and Man in the monosaccharide composition increased and the molecular weight decreased. When testing antioxidant activity in vitro, the ability of SE-pretreated HPS to scavenge DPPH radicals, hydroxyl radicals, and superoxide anion radicals was better than that of HPS without SE pretreatment. Our findings shed light on SE pretreatment as an efficient method for extracting active polysaccharides, providing a new way to improve their extraction rate and biological activity.

Vesicularity, Density, and Crystal Size Distribution of Pumice-Scoria at South-Southeast Flank of Merapi Volcano: A Window Into Explosive Volcanic Eruption

Abstract Merapi, one of the most active volcanoes in Java Island of Sunda Arc, is a constant threat to the ten million people who live within its 10-km radius of the summit. In 2010, it experienced an explosive eruptive event, sending pumice-laden pyroclastic density currents (PDC) that extended as far as 15 km down its southeastern flank. We report field observations of PDC deposits on the south-southeast flank of the volcano and calculate the vesicularity, density and crystal size distribution of pumice–scoria fragments. The density of the pumice–scoria is measured by archimedes’ principle by weighting the sample in water. The vesicularity is determined from petrography using the point counting method. Crystal Size distribution (CSD) is determined by images from thin sections using plagioclase crystals to calculate the magma residence time. Based on their physical appearance, the pumice–scoria fragments from this area are grouped into: (1) white pumice, (2) grey pumice, and (3) dark scoria. The density of white pumice is overlapping with the grey pumice group (1.5-2 g/ml); while the dark scoria is the densest among others (&gt;2 g/ml). The vesicularity of pumice–scoria ranges from 7-30%. CSD analysis is done in two most vesicular samples from each group. The CSD result gives both shallow and steep slopes which reflect the crystal size and population density. The slope suggests that magma residence times are (a) 11.49–249.68 years for grey pumice, (b) 5.03–194.54 years for white pumice, and (c) 3.83–273.36 years for dark scoria. This research suggests that the three types of pumice–scoria from the study area generally have similar crystallization path and time. Our CSD data shows that these pumice-scoria samples tend to have steeper slopes than lava samples, indicating a more uneven crystal-growth condition.

Observations of ionospheric disturbances associated with the 2020 Beirut explosion by Defense Meteorological Satellite Program and ground-based ionosondes

Abstract. A major explosion that released a significant amount of energy into the atmosphere occurred in Beirut on 4 August 2020. The energy released may have reached the upper atmosphere and generated some traveling ionospheric disturbances (TIDs), which can affect radio wave propagation. In this study, we used data from the Defense Meteorological Satellite Program (DMSP) and ground-based ionosondes in the Mediterranean region to investigate the ionospheric response to this historic explosion event. Our DMSP data analysis revealed a noticeable increase in the ionospheric electron density near the Beirut area following the explosion, accompanied by some wavelike disturbances. Some characteristic TID signatures were also identified in the shape of ionogram traces at several locations in the Mediterranean. This event occurred during a period of relatively quiet geomagnetic conditions, making the observed TIDs likely to have originated from the Beirut explosion, not from other sources such as auroral activities. These observational findings demonstrate that TIDs from the Beirut explosion were able to propagate over longer distances, beyond the immediate areas of Lebanon and Israel–Palestine, reaching the Mediterranean and eastern Europe.

Physicochemical properties of polysaccharides from Hericium erinaceus by steam explosion pretreatment and its effects on human gut microbiota

Crude polysaccharides (HEP) extracted from Hericium erinaceus (H. erinaceus) using hot water soaking were focused in this study. The effects of steam explosion (SE) pretreatment (against H. erinaceus raw material) on the physical and chemical characteristics and in vitro fermentability of HEP were examined. SE increased the yield, the total sugar content, and β-glucan content for HEP by 244.96%, 51.22% and 34.60%, respectively. SE treatment also reduced the molecular weight of HEP and released relative lower molecular fractions, as reflected by the elution profiles from HPSEC. During in vitro fermentation (by human feces) process, HEP from SE treated (HEQ) and untreated samples (HEW) both demonstrated capability in regulating gut microbiota (GM) by improving the abundance of beneficial bacteria such as Firmicutes and the production of short-chain fatty acids (SCFAs), while reducing the abundance of harmful bacteria such as Escherichia-shigella. Moreover, HEQ could increase the production of acetic, propionic and total SCFAs, while HEW could better increase the production of n-butyric acids. The findings of this study provide a reference for the efficient extraction and preparation of HEP, and highlighting its potential application in modulating GM.

Using Gabions to Protect Oil Storage Facilities from Damage

Purpose. During a drone explosion, debris is generated that poses a risk of damage to both humans and objects at an industrial site. Therefore, the main purpose of this study is to evaluate the effectiveness of using gabions with different fillers to reduce the risk of damage to the wall of an oil storage facility by debris generated during a drone explosion at an industrial site, as well as to analyze the value of the out-of-band velocity of the debris. Methodology. A numerical model based on the integration of the equation of motion of a material point was used to analyze the effectiveness of using gabions as protective structures of an oil storage facility during the flying of drone debris. The equations of motion of the debris are based on Newton's second law. This approach makes it possible to determine the unobstructed velocity of the fragment after passing the body of the protective barrier - the gabion. The developed numerical model takes into account the initial velocity of the fragment, its size, direction of movement, ejection height, and the material that fills the gabion body. On the basis of this numerical model, a computer program was created to conduct a computational experiment. Findings. An effective tool has been developed to analyze the risk of damage to the oil storage facility from the metallic impact of debris generated in the event of a drone explosion and to analyze the effectiveness of gabions. The results of computational experiments are presented. Originality. A fast-calculating numerical model has been built for the operational analysis of the efficiency of using gabions with different contents, which are used to protect an oil storage facility at an industrial site from the missile impact of debris generated by a drone explosion. Practical value. A computer program has been developed to calculate the dynamics of debris movement in the air and in the body of the gabion. The use of this program makes it possible to select the rational dimensions of a protective barrier - gabion at an industrial site to protect an oil storage facility from damage.

Middle Triassic basaltic pyroclastic rocks from the Mt. Medvednica ophiolitic mélange (NW Croatia): petrology, geochemistry and tectono-magmatic setting

Hectometric blocks of Middle Triassic mafic pyroclastic rocks, represented by volcanic agglomerates/breccias and lapilli tuffs, form part of the ophiolitic mélange of Mt. Medvednica, situated in the southwestern segment of the Zagorje-Mid-Transdanubian Zone. These rocks share petrochemical characteristics with pyroclastic derivatives of alkali, within-plate basaltic lavas of Mts. Medvednica, Samoborska Gora, and Kalnik, indicating the occurrence of explosive events preceding the dominant effusive submarine volcanism during the Middle Triassic (Illyrian-Fassanian?) stages. The formation of these pre-ophiolitic pyroclastics is associated with an intracontinental rift setting and reflects melts derived from an OIB-type enriched mantle plume source. These pyroclastics represent uncontaminated melts that erupted through a highly thinned continental crust. In geodynamic terms, the formation of pyroclastites occurred during the Late Anisian-Early Ladinian along the continental margin of Palaeotethys through the proto back-arc rifting of continental lithosphere (Adria Plate), leading to the formation of the Maliak/Balkan Neotethys Rift, in the emerging northwestern segment of Neotethys. The investigated pyroclastic rocks of Mt. Medvednica document the extension in an evolved intracontinental rift basin, which immediately preceded the generation of the initial Neotethyan oceanic lithosphere during the Upper Triassic.

INCREASING THE EFFECTIVENESS OF CIVIL PROTECTION BY THE DESIGN OPTIMIZING: THE REVIEW

Due to today's conditions, it is necessary to reconsider the purpose of buildings and structures that use a significant number of reinforced concrete elements subjected to complex stress-strain states. The researchers are faced with the task of determining the residual bearing capacity of an element with uneven damage, which will allow choosing the most optimal option for calculating and selecting materials. A detailed analysis of the most common damages to reinforced concrete structures, including protective structures and shelters, from the effects of explosives and weapons of various types was carried out to optimize and maintain strength and durability. It is also important to study the impact of damage that causes a stress-strain state that cannot be predicted by calculation.

Expected evolution of the binary system PTF J2238+743015.1

Binary systems harboring a low-mass CO WD and a He-rich donor are considered to be the possible progenitors of explosive events via He detonation, producing low-luminosity thermonuclear supernovae with a peculiar nucleosynthetic pattern. Recently, the binary system PTF J223857.11+743015.1 was proposed as a candidate for this kind of stars. We investigate the evolution of the PTF J223857.11+743015.1 system, which is composed of a 0.75\ CO WD and a 0.390\ subdwarf. We consider the rotation of the WD component. Using the FuNS code, we computed the evolution of the two stars simultaneously, taking into account the possible evolution of the orbital parameters, as determined by mass transfer between the components and by mass ejection from the system during episodes of Roche lobe overflow. We consider that the WD gains angular momentum due to accretion and we followed the evolution of the angular velocity profile as determined by angular momentum transport via convection and rotation-induced instabilities. As the donor H-rich envelope is transferred, the WD experiences recurrent very strong H-flashes triggering Roche lobe overflow episodes during which the entirety of the accreted matter is lost from the system. Due to mixing of chemicals by rotation-induced instabilities during the accretion phase, H-flashes occur inside the original WD. Hence, pulse by pulse, the mass of the accretor is reduced down to 0.7453\ Afterwards, when He-rich matter is transferred, He detonation does not occur in the rotating WD, which undergoes six very strong He-flashes and subsequent mass-loss episodes. Also in this case, due to rotation-induced mixing of the accreted layers with the underlying core, the WD is eroded. Later, as the mass-transfer rate from the donor decreases, a massive He buffer is piled up onto the accretor, which ends its life as a cooling WD. The binary system PTF J2238+743015.1 and all other binary systems with components of similar masses and similar orbital parameters are not good candidates as thermonuclear explosion progenitors.

Monitoring urban construction and quarry blasts with low-cost seismic sensors and deep learning tools in the city of Oslo, Norway

The aim of this study is to collect information about events in the city of Oslo, Norway, that produce a seismic signature. In particular, we focus on blasts from the ongoing construction of tunnels and under-ground water storage facilities under populated areas in Oslo. We use seismic data recorded simultaneously on up to 11 Raspberry Shake sensors deployed between 2021 and 2023 to quickly detect, locate, and classify urban seismic events. We present a deep learning approach to first identify rare events and then to build an automatic classifier from those templates. For the first step, we employ an outlier detection method using auto-encoders trained on continuous background noise. We detect events using an STA/LTA trigger and apply the auto-encoder to those. Badly reconstructed signals are identified as outliers and subsequently located using their surface wave (Rg) signatures on the seismic network. In a second step, we train a supervised classifier using a Convolutional Neural Network to detect events similar to the identified blast signals. Our results show that up to 87% of about 1,900 confirmed blasts are detected and locatable in challenging background noise conditions. We demonstrate that a city can be monitored automatically and continuously for explosion events, which allows implementing an alert system for future smart city solutions.