Vertical Plume Research Articles

JWST MIRI and NIRCam observations of NGC 891 and its circumgalactic medium

We present new JWST observations of the nearby, prototypical edge-on, spiral galaxy NGC 891. The northern half of the disk was observed with NIRCam in its F150W and F277W filters. Absorption is clearly visible in the mid-plane of the F150W image, along with vertical dusty plumes that closely resemble the ones seen in the optical. A $ kpc ^2$ area of the lower circumgalactic medium (CGM) was mapped with MIRI F770W at 12 pc scales. Thanks to the sensitivity and resolution of JWST, we detect dust emission out to $ 4$ kpc from the disk, in the form of filaments, arcs, and super-bubbles. Some of these filaments can be traced back to regions with recent star formation activity, suggesting that feedback-driven galactic winds play an important role in regulating baryonic cycling. The presence of dust at these altitudes raises questions about the transport mechanisms at play and suggests that small dust grains are able to survive for several tens of million years after having been ejected by galactic winds in the disk-halo interface. We lay out several scenarios that could explain this emission: dust grains may be shielded in the outer layers of cool dense clouds expelled from the galaxy disk, and/or the emission comes from the mixing layers around these cool clumps where material from the hot gas is able to cool down and mix with these cool cloudlets. This first set of data and upcoming spectroscopy will be very helpful to understand the survival of dust grains in energetic environments, and their contribution to recycling baryonic material in the mid-plane of galaxies.

Quantifying gas emissions through Vertical Radial Plume Mapping based on historical information

Vertical Radial Plume Mapping (VRPM) is a method for measuring fluxes of fugitive surface source gases, lacking sufficient temporal sequence information as it inversely calculates fluxes only based on the current cycle’s measurements. We propose an improved VRPM flux inversion model, incorporating Weighted Iterative Average (WIA) corrected Path-Integrated Concentration (PIC) and Adaptive Weighted Sum of Squared Errors (AWSSE). Compared to the original VRPM, our model introduces historical measurement PICs and reconstructed PICs. Using the Bayesian Optimization Gaussian Processes (BO-GP), we derive optimal weight factor for the hyperparameter of the WIA component in the model. Validation on simulated data highlights the superior flux inversion capability of the WIA-AWSSE-VRPM model across diverse surface sources, efficiently leveraging historical data. The improved VRPM method achieves a significant 9.65% reduction in root mean square error (RMSE) within consistent source sets and decreases RMSE from 1.6979 to 0.1513 across varied sources, underscoring its effectiveness in accurately measuring emissions from fugitive sources. Finally, we apply the model to characterize gas emissions in field experiments.

The characteristics of the vertical distribution of radionuclide in free troposphere from simplified release scenarios: a case study

Dose estimation in the upper air is not studied as much as on ground level or in boundary layer. However, there is a need from stakeholders in aviation industry for a reasonable estimation of the radioactive plume impact at cruising levels. This study aims to provide a quantitative estimation of the dose and how reliable it is for dispersion processes up to seven days. A Lagrangian atmospheric dispersion model is used to estimate quantitively the vertical extension of radionuclides from simplified hypothetical radionuclide release scenarios. Sources at different latitudes are selected for simulation in a boreal winter case. Three meteorological data are examined to test the sensitivity of vertical plume distribution to driving meteorological data. The vertical distribution of air concentration of radionuclides is investigated and the associated uncertainties are analysed. It is found that the vertical extension of plumes is sensitive to meteorological data being used where vertical turbulent velocities play an important role. It is therefore necessary to address the uncertainties of air concentration or dose in the free troposphere and caution must be taken when providing the results to stakeholders.

Influences of daily solar radiation intensity on the sea-land breeze and pollutant dispersion in coastal areas

Solar radiation plays a crucial role in the formation of sea-land breeze (SLB) circulation in coastal areas, and the SLB circulation in turn influences the atmospheric diffusion of pollutants in coastal cities. Therefore, the characteristics of the SLB and its impacts on the pollutant distributions in Shanghai, China, are numerically investigated for three (low, medium, and high) daily solar radiation intensities (DSRIs). The results show that the pollutant dispersion is affected by both the horizontal flow of SLB circulation and the vertical thermal plume (TP). The SLB only transports pollutants within the near-ground layer, while TP removes pollutants from the boundary layer and then improves near-ground air quality. Both the intensities of the SLB and TP increase with the increase of DSRI, however, the relative strength of the two are different at different DSRIs. When the DSRI is high (28.35 MJ/m2/day) or low (9.45 MJ/m2/day) during the daytime, the sea breeze (SB) is much stronger than the TP, so the prevailing flow direction on the land is horizontal, causing large amounts of pollutants to be blown inland. For the medium DSRI (18.90 MJ/m2/day), the TP is more powerful in the early stage of the SB period, so the airflow across the land is dominated by the rising TP. Pollutants are mainly transported to the upper atmosphere and the best air quality can be achieved in the residential region. At night, the worst air quality occurs at low DSRI, because when the DSRI is low, the speed of the land breeze is also low and this decelerates the diffusion of pollutants to the sea by the wind.

Large‐eddy simulation of plume dispersion in a turbulent boundary layer flow generated by a dynamically controlled recycling method

AbstractWhen conducting large‐eddy simulations (LESs) of plume dispersion in the atmosphere, crucial issue is to prescribe time‐dependent turbulent inflow data. Therefore, several techniques for driving LESs have been proposed. For example, in the original recycling (OR) method developed by Kataoka and Mizuno (Wind and Structures, 2002, 5, 379–392), a mean wind profile is prescribed at the inlet boundary, the only fluctuating components extracted at the downstream position are recycled to the inlet boundary. Although the basic turbulence characteristics are reproduced with a short development section, it is difficult to generate target turbulent fluctuations consistent with realistic atmospheric turbulence. In this study, we proposed a dynamically controlled recycling (DCR) method that is a simple extension of the OR procedure. In this method, the magnitude of turbulent fluctuations is dynamically controlled to match with the target turbulent boundary layer (TBL) flow using a turbulence enhancement coefficient based on the ratio of the target turbulence statistics to the computed ones. When compared to the recommended data of Engineering Science Data Unit (ESDU) 85020, the turbulence characteristics generated by our proposed method were quantitatively reproduced well. Furthermore, the spanwise and vertical plume spreads were also simulated well. It is concluded that the DCR method successfully simulates plume dispersion in neutral TBL flows.

A fast, physically based model of firebrand transport by bushfire plumes

Spotfires are a major problem in bushfire management, greatly complicate suppression efforts, and contribute to fires breaking control lines. Firebrands are often implicated in structure loss, and in extreme circumstances have been observed to ignite new fires over 30km ahead of the parent fire. Existing prediction techniques do not accommodate the problem of such long-range spotting, and the meteorological and fire conditions that lead to such events are not well understood. We present a computationally inexpensive, physically based model of ember transport within bushfire plumes, with four components: an integral plume model, a model of turbulence within the plume, a probabilistic model of ember transport by the plume, and a model of transport beneath the plume. The predicted ember landing distributions from this model compare satisfactorily to the explicit ember-transport calculations of Thurston et al. (2017) and to observations (Cruz et al., 2012). We examine the sensitivity of the simple model to its input parameters. The 90th percentile of spotting distance increases with increasing fire power and decreases with increasing ember terminal fall velocity and fire radius. Where there is a meteorological inversion or stable layer and the plume updraft is sufficiently strong to carry embers to that height, the stable layer substantially limits the transport distance, with increased height favoring longer-range transport. The effect of wind speed is complex, due to the competing factors of faster horizontal transport but suppressed vertical plume development with stronger winds.

Hydrodynamic modifications in vertical bubble plumes by a grid-screen

Air injection through a single circular nozzle has been used for aeration enhancement, oxygen transfer, and mixing in natural lakes and reservoirs. A series of laboratory experiments with different hydrodynamic conditions was carried out to improve mixing capacity and entrainment in vertically discharged bubble plumes. Hydrodynamic modifications were performed by inserting a grid-screen with different openings and distances from the nozzle and hydrodynamic modifications were examined for different air discharges. Bubble plume characteristics such as bubble concentration and velocity were measured along the vertical axis of the plume using an accurate Refractive Bubble Index (RBI) probe. Utilizing bubble concentration and bubble velocity data, the hydrodynamic forces such as buoyancy, drag, added mass, and surface tension were calculated before and after the grid-screen to evaluate modification by a grid-screen. The bubble induced force acting on the grid-screen was then calculated by implementing the momentum transfer at the vicinity of the grid-screen. The effects of grid-screen openings, the location of grid-screen respect to the nozzle, and air discharge on the contributed forces were examined to design the optimum operation condition. The results indicated that the grid-screen size and its distance from the nozzle decreased the buoyancy and drag forces after the grid-screen by 49% and 42%, respectively. Non-linear correlations between the hydrodynamic forces and bubble Reynolds number were proposed indicating that all contributing forces increased with increasing bubble Reynolds number. Empirical models were also developed for prediction of surface tension and bubble induced forces on the grid-screen.

Quantifying gas emissions through vertical radial plume mapping with embedded radial basis function interpolation

The Vertical Radial Plume Mapping (VRPM) method proposed by the U.S. EPA in Other Test Method 10 (OTM-10) is widely used to measure nonpoint source emissions. However, the accuracy of the VRPM is affected by the large number of parameters relative to the measurement data and the presence of measurement noise. To improve the accuracy of flux estimation, we propose to apply evenly spaced radial basis function (RBF) interpolation to the measurement data before using the VRPM. The experiment was tested and validated under various measurement configurations. The results indicate that RBF interpolation techniques, especially Gaussian RBF (GSRBF) interpolation, reduce the mean absolute error and root mean square error of flux estimation, leading to improved flux estimation accuracy. The mean emission rate calculated after RBF interpolation is closer to the true value, indicating that this interpolation technique helps to reflect more accurately the average emission level over time. Even in the most challenging validation set, the percentage error of mean flux decreased by 3.8% after interpolation. The proposed method can be a simple and measurement-cost-effective way to improve the accuracy of VRPM measurements.

Observation of Vertically Ejected Plumes Generated by the Impact of Hollow Projectiles at Various Velocities

Recently, impact experiments in space have been conducted in planetary exploration using hollow or internally structured projectiles. In laboratory experiments using hollow projectiles to investigate the differences in crater and ejecta from the case of solid projectiles, a plume perpendicular to the target surface has been observed, which has not been seen in conventional cratering experiments using solid projectiles. In this study, we conducted crater-formation experiments using hollow resin projectiles to understand the mechanism through which vertical plumes form in the case of hollow projectiles. We examined the generation of a vertical plume as a function of the impact velocity, v imp. We found that (i) no vertical plume occurs at v imp < 200 m s−1, (ii) the cases with or without a vertical plume are mixed at 200 < v imp < 350 m s−1, (iii) no vertical plume occurs at 350 < v imp < 800 m s−1, and (iv) a vertical plume occurs at 2 < v imp < 3 km s−1. We qualitatively discussed the generation mechanism of the vertical plume using the results of recovered projectiles. Depending on v imp, an empty hole in which there is no projectile materials can be opened along the central axis, resulting in the generation of a vertical plume.

Turbulent plumes above a heated plate

Our focus concerns the turbulent convective flow above a uniformly heated high-aspect-ratio rectangular plate on $z=0$ . Prior to this study, classic plume theory could not be applied directly as the Richardson number is ill-defined at the plate. Guided by observation, conservation equations are posed for the near-plate region where the attached buoyant flow is predominantly horizontal. Analytical solutions under the Boussinesq approximation reveal this to be a dynamically invariant region where the attached ‘plumes’ grow linearly toward the plate centreline, their merger forming an ‘apparent’ source for the vertical plume above. Coupling predictions with data from flow visualisation and temperature measurement, we deduce the half-width $0.72b_0$ , height ${z=0.46b_0}$ and finite Richardson number $({\sim }18)$ of an apparent source from which plume theory can be applied to model the plume above a heated plate of width $2b_0$ . Finally, practical implications of this advancement to the analytical theory of turbulent plumes are noted.

Modelling Plume Development with Annual Pulses of Contaminants Released from an Airport Runway to a Layered Aquifer, Evaluation of an In Situ Monitoring System

In cold climates, the use of de-icing chemicals in the winter can lead to groundwater contamination, especially when used in large quantities, such as at airports. Oslo Airport, Gardermoen, is situated on Norway’s largest rain-fed aquifer. Potassium formate is used to remove ice from runways and propylene glycol from airplanes; the organic parts are degradable. Most of the wells to monitor the spread of de-icing chemicals in the underlying aquifer have well screens near the groundwater level, while the runways and the source of de-icing chemicals are near the groundwater divides, where vertical flow is expected. The objective of this study is to demonstrate the importance of layers and time-varying recharge on the spreading of contaminant plumes in an aquifer near a groundwater divide. This is done with numerical modelling. The model results show increased vertical transport of the added tracer in the presence of horizontal layers, both continuous and discontinuous, in the aquifer. With certain distributions of hydraulic conductivity, Ks, we demonstrate that deeper monitoring wells are required. With the scenarios modelled here, time-varying recharge has a weaker effect on plume distribution. Measured concentrations of potassium and total organic carbon show the cyclic effect of seasonally varying recharge of contaminants, and an asymptotic accumulation of concentration over time, that is consistent with the model runs. In conclusion, groundwater monitoring systems near a groundwater divide should include multi-level samplers to ensure control of the vertical plume movement.

Effects of air discharge on bubble dynamics in vertically discharged bubble plumes

Vertically discharged bubble plumes have many applications in the industry and environment, such as aeration and sludge removal, gas and liquid mixture, and gas transfer enhancement. Circular nozzles mainly generate vertical bubble plumes and the ambient aeration requirement determines the design parameters such as nozzle size and air discharge. A series of laboratory experiments was performed to test the effects of air discharge on bubble dynamics by evaluating, bubble interfacial area, bubble size frequency, and other related parameters. Four air discharges were selected and bubble characteristics such as bubble mean velocity, bubble concentration, bubble mean diameter, and bubble size distribution were measured with a Bubble Refractive Instrument (RBI) probe. The results showed that bubble characteristics such as bubble interfacial area, bubble frequency, and bubble concentration/gas fraction significantly varied with the distance from the nozzle and all parameters gradually decreased afterwards. It was found that bubble parameters were independent of air discharge for x/H < 0.35, and strong discharge dependency was observed for x/H ≥ 0.35 where × is the distance from the nozzle and H is the water depth. Experimental results indicated that as air discharge increased by four times, the mean bubble diameter increased by an average of 32 %. The direct correlation between air discharge and bubble frequency indicated that both the number of bubbles and their velocities increased non-linearly with air discharge. The effect of air discharge on the distribution of bubble turbulent intensity indicated a non-linear growth on the probability of higher ranges of turbulent intensity.

Phytoplankton transport out of the euphotic zone by frontal subduction and gravitational sinking in the Santa Barbara Channel, CA, USA

Production of particulate organic carbon (POC) in nutrient-rich coastal waters over continental shelves, its export to depth, and its transport to deeper ocean waters is a poorly quantified component of the global carbon cycle. A critical step in quantifying this vertical transport is identifying shelf processes that export phytoplankton out of the euphotic zone. During cruises of the Santa Barbara Coastal Long Term Ecological Research project, we discovered substantial chlorophyll a (chl a) below the euphotic zone in the Santa Barbara Channel, a part of the southern California Current System. Observations from towed, undulating vehicles revealed deep chlorophyll layers near fronts where upwelled waters from central California converged with lower-density waters from the Southern California Bight. The mean fraction ± 1 standard deviation (SD) of chlorophyll biomass below the euphotic zone spanning the entire Santa Barbara Channel was ~7 ± 9% during 13 cruises averaged across all seasons. In one spring cruise, the fraction was ~30%, and in other cruises the layers were absent. Phytoplankton export out of the euphotic zone by subduction was indicated by spatial coherence between chl a and sloping density surfaces. Vertical plumes of chl a crossing density surfaces indicated enhanced gravitational export within cyclonic eddies. Chl a in water samples below the euphotic zone, away from fronts and cyclonic flows, suggested additional phytoplankton export. Our results emphasize the importance of subduction in the export of phytoplankton and POC out of the euphotic zone in coastal upwelling systems.

Full-scale experimental and numerical study of smoke spread characteristics in a long-closed channel with one lateral opening

This paper aims to study the characteristics of smoke flow in a long-closed channel with one lateral opening at one end. A series of full-scale experiments with different longitudinal positions and heat release rates of fire sources were carried out. And, the corresponding numerical simulations were conducted to help explain the law of smoke flow field. The characteristics of the smoke spread on both sides of the fire source, the thermal plume distribution within the channel, and the maximum ceiling excess temperature were analyzed. Results show that the existence of the end walls in the long channel causes the smoke to accumulate, which further results in the smoke settlement going through three stages. The lateral opening causes a significant difference of smoke flow and other characteristics from the channel with both ends open. When the fire source approaches the closed end without opening, the vertical fire-induced plume inclines to the closed end because of the asymmetrical air supplementation. Due to the limited air supply, the combustion will change to ventilation-controlled as the fire source heat release rate increases. The maximum ceiling excess temperature is higher than that with both ends open and is basically not influenced by fire positions studied in this work. It has been verified that the dimensionless maximum ceiling excess temperature of the smoke is also proportional to the dimensionless heat release rate. This study can provide a reference for fire prevention and smoke exhaust strategies for long channels.

Surface-to-space atmospheric waves from Hunga Tonga–Hunga Ha’apai eruption

The January 2022 Hunga Tonga–Hunga Ha’apai eruption was one of the most explosive volcanic events of the modern era1,2, producing a vertical plume that peaked more than 50 km above the Earth3. The initial explosion and subsequent plume triggered atmospheric waves that propagated around the world multiple times4. A global-scale wave response of this magnitude from a single source has not previously been observed. Here we show the details of this response, using a comprehensive set of satellite and ground-based observations to quantify it from surface to ionosphere. A broad spectrum of waves was triggered by the initial explosion, including Lamb waves5,6 propagating at phase speeds of 318.2 ± 6 m s−1 at surface level and between 308 ± 5 to 319 ± 4 m s−1 in the stratosphere, and gravity waves7 propagating at 238 ± 3 to 269 ± 3 m s−1 in the stratosphere. Gravity waves at sub-ionospheric heights have not previously been observed propagating at this speed or over the whole Earth from a single source8,9. Latent heat release from the plume remained the most significant individual gravity wave source worldwide for more than 12 h, producing circular wavefronts visible across the Pacific basin in satellite observations. A single source dominating such a large region is also unique in the observational record. The Hunga Tonga eruption represents a key natural experiment in how the atmosphere responds to a sudden point-source-driven state change, which will be of use for improving weather and climate models.

Effects of vertical ship exhaust plume distributions on urban pollutant concentration – a sensitivity study with MITRAS v2.0 and EPISODE-CityChem v1.4

Abstract. The modeling of ship emissions in port areas involves several uncertainties and approximations. In Eulerian grid models, the vertical distribution of emissions plays a decisive role for the ground-level pollutant concentration. In this study, model results of a microscale model, which takes thermal plume rise and turbulence into account, are derived for the parameterization of vertical ship exhaust plume distributions. This is done considering various meteorological and ship-technical conditions. The influence of three different approximated parameterizations (Gaussian distribution, single-cell emission and exponential Gaussian distribution) on the ground-level concentration are then evaluated in a city-scale model. Choosing a Gaussian distribution is particularly suitable for high wind speeds (&gt;5 m s−1) and a stable atmosphere, while at low wind speeds or unstable atmospheric conditions the plume rise can be more closely approximated by an exponential Gaussian distribution. While Gaussian and exponential Gaussian distributions lead to ground-level concentration maxima close to the source, with single-cell emission assumptions the maxima ground-level concentration occurs at a distance of about 1500 m from the source. Particularly high-resolution city-scale studies should therefore consider ship emissions with a suitable Gaussian or exponential Gaussian distribution. From a distance of around 4 km, the selected initial distribution no longer shows significant differences for the pollutant concentration near the ground; therefore, model studies with lower resolution can reasonably approximate ship plumes with a single-cell emission.

Wildfire Smoke Observations in the Western United States from the Airborne Wyoming Cloud Lidar during the BB-FLUX Project. Part II: Vertical Structure and Plume Injection Height

Abstract The western U.S. wildfire smoke plumes observed by the upward-pointing Wyoming Cloud Lidar (WCL) during the Biomass Burning Fluxes of Trace Gases and Aerosols (BB-FLUX) project are investigated in a two-part paper. Part II here presents the reconstructed vertical structures of seven plumes from airborne WCL measurements. The vertical structures evident in the fire plume cross sections, supported by in situ measurements, showed that the fire plumes had distinct macrophysical and microphysical properties, which are closely related to the plume transport, fire emission intensity, and thermodynamic structure in the boundary layer. All plumes had an injection layer between 2.8 and 4.0 km above mean sea level, which is generally below the identified boundary layer top height. Plumes that transported upward out of the boundary layer, such as the Rabbit Foot and Pole Creek fires, formed a higher plume at around 5.5 km. The largest and highest Pole Creek fire plume was transported farthest and was sampled by University of Wyoming King Air aircraft at 170 km, or 2.3 h, downwind. It was associated with the warmest, driest, deepest boundary layer and the highest wind speed and turbulence. The Watson Creek fire plume intensified in the afternoon with stronger CO emission and larger smoke plume height than in the morning, indicating a fire diurnal cycle, but some fire plumes did not intensify in the afternoon. There were pockets of relatively large irregular aerosol particles at the tops of plumes from active fires. In less-active fire plumes, the WCL depolarization ratio and passive cavity aerosol spectrometer probe mass mean diameter maximized at a height that was low in the plume.

Assessing Impacts on Pressure Stabilization and Leasing Acreage for CO2 Storage Utilizing Oil Migration Concepts

Favorable geological storage for CO2 has long been pictured as large anticlines with thick sandstones, similar to oil reservoirs in the petroleum system. Unlike oil, however, stored CO2 does not need to be recoverable, which raises the possibility of using dissolution and residual trapping to augment the capacity of buoyant traps and tap more of the bulk rock volume. The work presented builds on that idea, asking the following question: If we inject CO2 down to a syncline – analogous to the carrier bed in the petroleum system – how would this injection mechanism impact storage capacity and plume shape, migration, and stabilization? To address this question, we built a reservoir model, based on seismic interpretation of Middle Miocene strata, offshore Galveston, Texas. 3-D seismic and well logs were used to characterize key intervals. Reservoirs chosen for modeling are progradational-aggradational sands with mud intercalation. They have a higher degree of heterogeneity than the more conventional reservoirs commonly targeted for CO2 storage. Modeling investigated how far the CO2 plume would migrate under two scenarios: (1) injecting CO2 at the base of the salt withdrawal basin (syncline scenario) and (2) injecting CO2 at the base of the structural closure, similar to a common injection well location for EOR purposes (base scenario). For each scenario, we separately simulated injection of 30 MT of CO2 and 60 MT of CO2 continuously for 30 years and observe the plume and pressure evolution for 100 years after the injection stops. The simulation shows that injecting the CO2 into a syncline limits the vertical migration of CO2, thus making synclinal injection more secure. In the syncline scenario, the geological layer around the injection point is more heterogeneous than the layer in the base scenario; thus, the CO2 tends to migrate laterally. Additionally, in the syncline scenario, the plume does not even reach the upper part of the anticline, allowing us to safely store an additional amount of CO2 into the reservoir. Moreover, the simulation also shows that in the syncline scenario, the times needed for the reservoir to reach its stabilized pressure after the end of injections are faster. To summarize, CO2 injection at the base of a syncline could provide additional storage, increase the safety of the project from the limited vertical plume migration, and expedite plume stabilization, which could result in the decrease of monitoring frequency as the project runs, thus lowering the operating cost of the project in the long run.

3D Field-Scale Geomechanical Modeling of Potential CO2 Storage Site Smeaheia, Offshore Norway

Injection-induced rock mechanical failure risks are critical in CO2 sequestration, and thus there is a need to evaluate these occurrences to ensure safe and reliable subsurface storage. A stress–strain-based numerical simulation can reveal the potential mechanical risks of any CO2 sites. This study investigated the hydromechanical effect on geomechanical failure due to injection-induced stress and pore pressure changes in the prospective CO2 storage site Smeaheia, offshore Norway. An inverted-seismic-property-driven 3D field-scale geomechanical model was carried out in the Smeaheia area to evaluate the rock failure and deformation risks in various pressure-build-up scenarios. A one-way coupling between the before- and after-injection pressure scenarios of nine different models has been iterated using the finite element method. The effect of the sensitivity of total pore volume and pore compressibility on rock mechanical deformation is also evaluated. Although various models illustrated comparative variability on failure potential, no model predicted caprock failure or fracture based on the Mohr–Coulomb failure envelope. Moreover, the lateral mechanical failure variation among different locations indicated the possibility to identify a safer injection point with less chances of leakage. In addition, the pore volume and pore compressibility significantly influence the mechanical behavior of the reservoir and caprock rocks. Although this analysis could predict better injection locations based on geomechanical behavior, a fluid simulation model needs to be simulated for assessing lateral and vertical plume migration before making an injection decision.

Strong ULVZ and Slab Interaction at the Northeastern Edge of the Pacific LLSVP Favors Plume Generation

AbstractStrong waveform complexities, including multipathing of the S diffracted phase and rapid changes in differential ScS‐S times, are observed for multiple deep Fiji earthquakes recorded at the USArray. The complexities occur at the northeastern edge of the Pacific Large Low Shear Velocity Province (LLSVP), about 12 degrees southeast of present‐day Hawaiʻi. Waveform modeling of the multipathing provides good constraints on an ultra‐low velocity zone (ULVZ) with a width of 5 degree located near the inner edge of the LLSVP. Based on the mineralogical‐modeling of the ULVZ as a solid iron‐rich magnesiowüstite‐bearing assemblage with compatible morphology predicted from geodynamical simulations, a ULVZ model with a thickness of 30 km and a shear wave velocity reduction of 18% is preferred. The rapid change in differential ScS‐S travel time is best explained by having both the aforementioned ULVZ and an adjacent high velocity structure near the LLSVP. Furthermore, a low‐velocity plume‐like structure could potentially explain the observed S travel time delay independent of ScS. These seismic features are proposed to be a ULVZ driven toward the edge of the LLSVP while potentially pushed by a subducted slab. This configuration may trigger plume generation due to strong thermal instabilities and is in the same vicinity where mantle flow models place the present‐day Hawaiian plume source. Multiple ScS can potentially be used to verify vertical plume structure in tomographic models but the accuracy of upper mantle structure, which is a key reflection point, needs to be considered.