Shear Stress Drop Research Articles

The effect of torus tubarius size on upper airway aerodynamics in children: a computational fluid dynamics study.

Some children with sleep-disordered breathing (SDB) continue to experience symptoms after adenotonsillectomy. One possible cause is the excessive size of the torus tubarius. In this study, the relationship between torus tubarius size and surgical outcome in 24 children with SDB who underwent adenotonsillectomy was retrospectively analyzed based on cone beam computed tomography (CBCT) imaging measurements and medical records. A computational fluid dynamics (CFD) approach was used to quantitatively compare the effects of different torus tubarius sizes on upper airway (UA) aerodynamics in children. The percentage of UA area occupied by the torus tubarius (TTA%) was significantly different between the excellent and poor groups (10.4 ± 3.58% vs. 17.71 ± 4.7%, p < 0.001). The results of CFD simulation showed that the mean airflow velocity, wall shear stress (WSS) and pressure drop (ΔP) in the nasopharynx significantly increased when the TTA% was > 15%. Our study confirmed the effect of round pillow size on the aerodynamics of the UA in children. When the TTA% exceeds 15%, it causes change in aerodynamics, which may affect the outcome of children with SDB.

Effect of displacement loading rate on dynamic mechanical characteristics of fault stick-slip under constant normal stiffness conditions

The role of the displacement loading rate in fault activation and evolution is of utmost importance, yet most existing studies have primarily focused on its effect under constant normal load (CNL) conditions. However, in reality, the rock mass surrounding the earthquake source at the deep part of the fault provides normal stiffness conditions. Therefore, the influence of the displacement loading rate on the dynamic mechanical characteristics of fault stick-slip under constant normal stiffness (CNS) conditions remains uncertain. To bridge this research gap, we conducted an experimental investigation on simulated faults in granite under constant normal stiffness (CNS) conditions. Our analysis focused on the influence of the displacement loading rate on the spatial and temporal evolution of local stresses along the fault and the size of the fault nucleation zone. The findings revealed the following: Under the CNS condition, the equivalent shear stress is larger compared to the CNL condition, while the shear stress drop is smaller. The recovery of normal stress under CNS conditions depends more on the displacement loading rate. The nucleation location of the fault is influenced by the normal boundary conditions, with a larger nucleation zone observed in the CNS condition than in the CNL condition. In the early stage of friction, the local stress and stress drop of the fault exhibit a positive correlation with the displacement loading rate, whereas in the later stage, they display a negative correlation. Moreover, at the same location, the order of local stress drop rates for the fault is v3 &gt; v1 &gt; v2, where v1 represents the local normal stress drop rate, v2 represents the local shear stress drop rate and v3 represents the local friction coefficient drop rate. These research results contribute to a further understanding of the deep fault-slip mechanical behavior.

Frictional Properties of Simulated Fault Gouges Subject to Normal Stress Oscillation and Implications for Induced Seismicity

AbstractUnder critical conditions where experimental fault slip exhibits self‐sustained oscillation, effects of normal stress oscillation (NSO) on fault strength and stability remain poorly understood, as do potential effects of NSO on natural and induced seismicity. In this study, we employed double direct‐shear testing to investigate the frictional behavior of a synthetic, slightly velocity‐weakening (SVW) fault gouge (characterized by self‐sustained oscillation under quasi‐static shear loading), when subjected to NSO at different amplitudes (5%–20% of 5 MPa) and frequencies (0.001–1 Hz). During the experiment, fault displacement and gouge layer thickness were measured. Transmitted ultrasonic waves were also employed to probe grain contact states within the gouge layer. Our results show that fault weakening and unstable slip can be triggered at NSO frequencies ranging from 0.03 to 0.1 Hz and amplitudes exceeding 5%. Interestingly, an amplified shear stress drop and weakening effect were observed when the NSO frequency fell in 0.05–0.1 Hz. Analysis of transmitted ultrasonic waves in tests on the SVW gouge revealed fault dilation, accompanied by unstable slip and weakening. By extending an existing microphysical model (the “Chen‐Niemeijer‐Spiers [CNS]” model), to account for elastic effects of NSO on gouge microstructure and grain contact state, the mechanical and wave data obtained in our experiments on the SVW gouge was reproduced, suggesting an approach for modeling fault instability under upper crustal (SVW) conditions where normal stress is perturbed by subsurface operations, such as periodic gas storage stimulation of reservoir formations.

Comprehensive analysis of Chinese hamster ovary cell viability loss in mini-hydrocyclones

Mini-hydrocyclones are gaining popularity as effective tools for cell retention in perfusion cultivation. As the most widely used mammalian cell for cultivation, Chinese hamster ovary (CHO) cells experience a decline in viability after passing through mini-hydrocyclones. The reasons behind the cell viability loss within mini-hydrocyclones are not understood. This study aims to comprehensively examine the cell viability loss in relation to shear stress and pressure drop through a combination of experimental analysis and numerical simulations. The results show that a larger hydrocyclone conical factor or spigot diameter decreases pressure drop and shear stress, resulting in a lower cell viability loss. To evaluate the dependence of cell viability loss on shear stress and pressure drop, a correlation model is developed and a sensitivity analysis is performed. The results show that mean shear stress has the greatest impact on cell viability loss, followed by pressure drop and maximum shear stress.

Fractal Spatial Distributions of Initial Shear Stress and Frictional Properties on Faults and Their Impact on Dynamic Earthquake Rupture

ABSTRACT We investigate the influence of the heterogeneous slip-weakening distance (DC) in dynamic rupture simulations, in which DC is proportional to the fault irregularities. Specifically, we compare a heterogeneous fractal DC distribution to a uniform DC over the entire fault when the initial shear stress is also heterogeneous. We find that even small changes in the average value of DC (&amp;lt;1 mm) can lead to significant differences in the rupture evolution; that is, the average DC and the way DC is distributed determines if the rupture is a runaway, self-arrested, or nonpropagating. We find that the self-arrested ruptures differ from runaway ruptures in the amount of area characterized by large slips (asperities). Self-arrested ruptures match the Somerville et al. (1999) asperity criteria in which ∼25% of ruptured area radiate ∼45% of the total seismic moment. This criterion is not satisfied for runaway ruptures. For runaway ruptures, ∼50% of the ruptured area radiates about 70% of the seismic moment, indicating that the ruptured area is not linearly proportional to the seismic moment. Self-arrested ruptures are characterized by dynamic shear stress drops (SDs) in the range ∼2.9–5.5 MPa, whereas for runaway ruptures the dynamic SDs increase to values between ∼12 and 20 MPa. Self-arrested ruptures generated by fractal distributed DC resemble the rupture properties of observed earthquakes. In addition, results show that the conditions for self-arrested ruptures are connected to the decrease of residual energy at rupture boundaries.

Cryogenic thermal cycling effects on serration behavior in wide glass transition temperature Zr-based bulk metallic glasses

Serration behavior serves as a pivotal link connecting micro-deformation mechanism to the mechanical properties of metallic glasses. To elucidate the impact of cryogenic thermal cycling (CTC) and compositional modifications on metallic glasses’ serration behavior, a series of Zr-based metallic glasses, exhibiting a broad range of glass transition temperatures (Tg), were meticulously manufactured. The stress drop magnitude initially decreases before the peak-rejuvenation induced by CTC, then gradually increases, while the number of stress drops exhibits an initial increase and then a decrease. These trends correlate with optimized plasticity of the metallic glasses. Remarkably, metallic glasses with lower Tg predominantly undergo strain hardening during plastic deformation. They exhibit lower viscosity in shear band zones and stress drop compared to others, attributed to the temperature increase around shear band zones approaching Tg. This phenomenon promotes shear band activation in smaller flow units, leading to finer serrations compared to glasses with higher Tg.

Effects of size, geometry, and testing temperature on additively manufactured Ti-6Al-4V titanium alloy

This article presents a comprehensive study concerning size and geometry effect on the ambient and high-temperature mechanical behavior of additively manufactured laser powder bed fusion Ti-6Al-4V alloy. Key mechanical property metrics are presented, including strain hardening rate, yield strength, and Young’s modulus as a function of thickness and testing temperature (ambient, 250 °C, and 450 °C). The effect of specimen size on manufacturing-induced microstructural feature formation is demonstrated and discussed. A detailed analysis regarding Young’s modulus, yield strength, and strain hardening rate variation at elevated temperatures is also presented. Size effect and temperature-sensitive deformation mechanisms are linked to the underlying microstructural deformation mechanisms activated at respective temperatures. Counter-intuitively, this study determined that irrespective of the geometry, strain hardening rates increased as temperature increased. An in-depth microstructural examination is presented to explain the stated observation. The texture of Interrupted tensile test samples examined for ambient, 250 °C, and 450 °C post-yield was observed to be unchanged, indicating the strain hardening behavior was not texture dependent. Schmid factor analysis, coupled with experimental findings from previous work, was implemented to generate a hypothesis. This hypothesis suggests that the drop in critical resolved shear stress for basal and pyramidal slip systems, as temperature increases, paired with the high dislocation density of laser powder bed fusion Ti-6Al-4V, leads to dislocation entanglement and results in increased strain hardening at elevated temperatures.

Nucleation Mechanism and Rupture Dynamics of Laboratory Earthquakes at Different Loading Rates

The loading rate of tectonic stress is not constant during long-term geotectonic activity and significantly affects the earthquake nucleation and fault rupture process. However, the mechanism underlying the loading rate effect is still unclear. In this study, we conducted a series of experiments to explore the effect of the loading rate on earthquake nucleation and stick–slip characteristics. Through lab experiments, faults were biaxially loaded at varying rates to produce a series of earthquakes (stick–slip events). Both shear strain and fault displacement were monitored during these events. The findings indicate a substantial effect of the loading rate on the recurrence interval and the shear stress drop of these stick–slip events, with the recurrence interval inversely proportional to the loading rate. The peak friction of the fault also decreases with the increasing loading rate. Notably, prior to the dynamic rupture of earthquakes, there exists a stable nucleation phase where slip occurs in a quasi-static manner. The critical nucleation length, or the distance required before the dynamic rupture, diminishes with both the loading rate and normal stress. A theoretical model is introduced to rationalize these observations. However, the rupture velocity of these lab-simulated earthquakes showed no significant correlation with the loading rate. Overall, this study enhanced our comprehension of earthquake nucleation and rupture dynamics in diverse tectonic settings.

Prediction of interfacial shear stress and pressure drop in vertical two-phase annular flow

The interfacial shear stress and pressure drop of an upward vertical annular flow of nitrogen–water, HFC134a–water, and nitrogen–95 % ethanol solution were comprehensively investigated considering the effect of the liquid–gas density ratio and surface tension. A direct link between the disturbance wave height and equivalent sand-grain roughness was noted through the analogy with the famous Moody chart for single-phase turbulent flows. A predictive model of the interfacial friction factor was developed based on this finding. To predict the pressure drop of the annular flow, a new model with good predictive performance for annular flows of various working fluids including steam–water under boiling water reactor operating condition (286 °C and 7 MPa) was proposed.

3D modeling and simulation of an alkaline flow battery considering the tertiary current distribution on the electrodes: Anthraquinone-ferro/ferricyanide as organic electroactive species

A 3D-mathematical model in steady-state for an alkaline organic redox flow battery with an interdigitated channel is proposed based on the Nernst-Planck and Butler-Volmer theories, as well as the tertiary current distribution model. One of the main objectives of this study is considers the role of the inlet and outlet manifolds on the AORFB performance. The simulation results show a good prediction of the experimental polarization curves at different SOCs (10%, 50% and ∼100%) using the 2,6-dihydroanthraquinone/ferrocyanide redox couple at laboratory scale cell. Specifically, at a state of charge of 10% and cell voltage of 1.2 V, the model described adequately the relationship between ion concentration and cell overpotential due to considers the resistances to mass transfer at the electrode-electrolyte interface by means of the mass transfer coefficient model. In present work, it is show that the inlet manifold (dividing type) causes an electrolyte flow maldistribution along the channels and from channel to channel, provoking local zones whit greater shear stress and pressure drop, as well as zones with high concentration, and as consequence zones with high current densities and potential drops, which could lead to a more rapid deterioration of the cell components decreasing the useful life of the AORFB or that the charge-discharge efficiency cycles decrease over time of operation. These results cannot be observed in 2D simulations using a small repeating unit or unit cell.

The Pressure‐ and Temperature‐Dependence of Thermal Pressurization in Localized Faults

AbstractThermal pressurization (TP) is predicted to be an important dynamic frictional weakening mechanism during earthquakes. The prevailing models, though, assume that the physical, thermal and hydraulic properties of the fluid‐saturated rock in the fault zone are constant during TP (the constant case) which inherently involves temperature and pressure changes. We solve the governing equations for TP in their general form with pressure‐ and temperature‐dependent physical, thermal and hydraulic parameters of a saturated fault zone with a one‐dimensional numerical model (the variable case). The model considers slip on a plane at a constant rate, and so does not account for dynamic frictional rupture scenario. We test a wide range of medium permeabilities of 10−22–10−16 m2 and porosities 0.5%–17%, based on experimental data for Frederick diabase, Westerly granite and the Hanaore Fault gouge. We find that the predicted shear stress drop and temperature rise is similar between the two cases for low permeability (&lt;10−20 m2) and low porosity (&lt;1%) fault rocks, owing to an increase in the fluid pressurization factor and hydraulic diffusivity. Differences between the two models are evident in more permeable and porous fault rocks. The increase in hydraulic diffusivity during TP results in a diffusional length which scales with time0.7 in the variable case. In addition, our calculations show that it is important to apply the constant case model with the ambient initial conditions for the modeled fault zone and not time‐averaged values that aim to represent the temperature and pressure changes that occur during TP.

Unstable Shear Slip Failure and Seismic Potential Investigation Using DEM in Underground Mining

Perturbations arising from mining operations significantly affect the stability of rock masses, and the influences aggerates with the rapid increase of mining-operation depths during recent years. The subsurface structures with major discontinuities subject to seismic hazards resulted from the shear-slip behaviors of rock masses. In order to identify the shear-slip regime of discontinuities and calculate seismic moment and seismic energy involved with shear-slip behaviors, we use discrete element modeling to study the shear slip failure along discontinuities in an underground mine. The recorded characteristic and properties of sub-contacts in DEM provide a basis for computing and visualizing the temporal and spatial distribution of seismic moment and seismic energy with mining operations. We computed the seismic energy and seismic moment using the numerical modeling method and the analytic method. We compared the result of summing seismic energy and seismic moment from the subcontacts of numerical models and the result of the analytic method. We confirmed that this tool can be used in comparative analyses. We also found that seismic moment and seismic energy, associated with shear stress drop and shear displacement increase, accumulate in the vicinity of major discontinuities. Mining operations at a greater depth cause greater changes of seismic moment and seismic energy, leading to a higher risk of inducing seismic hazards. Quantifying seismic potential using discrete element modeling can greatly facilitate the investigation of instability of geological discontinuities and thereby can help estimate the potential of seismic hazards.

Laboratory study of the effects of grouted rebar bolts on shear failure of structural planes in deep hard rocks

Rock hazards induced by shear slip along discontinuities are often encountered in deep hard rock excavations. At present, grouted rebar bolts are still the most widely used supporting tools in underground engineering. However, as the in-situ stress increases, the anchoring effect of bolts on rock discontinuities change significantly compared with that in a shallow environment. It is of great significance to study the influence of rebar bolts on the shear failure characteristics of structural planes under high stress to ensure the safety of engineering construction at deeper depths. In this study, shear tests were conducted on split granite structural planes secured with bolts under various normal stresses to investigate the supporting effect of the rebar bolts on the hard rock structural planes under high stress. The stress, deformation, acoustic emission, and rock failure characteristics in the tests were fully investigated and analyzed, and the effects of the rebar bolts on the dynamic failure of the hard rock structural plane and a simplified model were investigated through comparison with the shear failure characteristics of unreinforced granite joints. The experimental results show that when a bolt is inserted through a highly stressed granite structural plane, before the bolt fractures, it can change the slip mode of the structural plane from stick-slip to stable-slip, which effectively delays the occurrence of shear-induced dynamic failure. After the bolt fractures, the interaction between the bolt and structural plane causes the stress drop events to increase, but it greatly weakens the energy emitted by a single shear stress drop, thus effectively reducing the intensity and destructiveness of the dynamic failure during shearing. The findings of this study have significant implications for the management and control of structural-slip rock hazards in deep rock tunnels.

Hydrogeotechnical Predictive Approach for Rockfall Mountain Hazard Using Elastic Modulus and Peak Shear Stress at Soil–Rock Interface in Dry and Wet Phases at KKH Pakistan

Predicting the susceptibility of rockfall mountain hazards for block-in-matrix soils is challenging for critical steep cuts. This research illustrates a hydrogeotechnical approach for the prediction of rockfall triggering by performing laboratory tests on low-cohesive-matrix soil collected from steep slopes with 85° to 88° angles at the Tatta Pani site, Karakorum Highway (KKH), and then real-scale moisture-induced rockfall was conducted on site for the validation of laboratory data. Laboratory data of forty quick direct shear tests on samples collected from the field depicted a 3-fold drop in peak shear stress (PS) at the soil–soil interface and a 9.3-fold drop at the soil–rock interface by varying the moisture content from 1% (taken as dry phase) to a critical laboratory moisture content (MC)LC of 21% (taken as wet phase). Similarly, a drop in the elastic modulus (ES) was observed to be 5.7-fold at the soil–soil interface and 10-fold at the soil–rock interface for a variation of moisture content from 1 % to 21% for the matrix with a permeability (k) range of 3 × 10−4 to 5.6 × 10−4 m/s, which depicts the criticality of moisture content for the rockfall phenomenon. The critical moisture content evaluated in laboratory is validated by an innovative field-inundation method for thirty-two moisture-induced real-scale forced rockfall cases, which showed the rock-block triggering at field dry density (γd)f and the critical field moisture content (MC)FC of the matrix ranging from 1.78 g/cm3 to 1.92 g/cm3, and 1.3% to 25.4%, respectively. Hydrogeotechnical relations, i.e., MC versus PS and ES, at the soil–rock interface are developed for the prediction of rockfall triggering. The proposed correlations may be helpful in the prediction of rockfall hazards by using expected rainfall in the field for disaster warning and landslide disaster prevention at ecological geotechnical engineering projects. The results revealed that the critical (MC)FC and (MC)LC are within 20%, depicting a good confidence level of the outcomes of this research.

Shear transformation zones and serrated flow dynamics of metallic glasses revealed by nanoindentation

The relationship between shear transformation zones (STZs) and serrated flow dynamics of Co-, Fe-, Zr-, La- and Al-based metallic glasses (MGs) with different plasticity were analyzed by nanoindentation. The serrated flow dynamic behaviors were analyzed using statistical analysis of shear stress drops, Δτ. The STZ size was estimated via the nanoindentation creep method based on the cooperative shear model. Examination of two distinct types of serrated flow dynamics were performed. For MGs (e.g., Al- or Zr-based) where STZs could be easily activated or at low loading rates, shear stress exhibited a decreasing trend and followed a power-law distribution, which was an indicator of a self-organized critical (SOC) state in the dynamics. In contrast, a Gaussian law distribution was found for STZs in hard MGs (e.g., La-, Co-, and Fe-based) or at high loading rate. In the case of Gaussian distribution case, serrated flow dynamics were in a chaotic state, which indicated that STZ aggregation reduced the stresses required for plastic deformation.

The side stream and different spacers effects on the permeate water flux in forward osmosis process using computational fluid dynamics

Forward osmosis (FO) is a membrane-based process that has an important application in water desalination. However, there are challenges in making this method operational on an industrial scale. This paper investigated a new spacer based on the concept of airfoils and the use of an optimized side stream to increase turbulency and water flux in the FO process. The effect of seven different spacer types and the side stream was investigated using computational fluid dynamics (CFD) and the design of experiment (DOE) techniques. The results showed that when an airfoil spacer was used, the water flux decreased along the membrane with a very slight slope (about 54% less than the base state). Also, the local water flux will increase by about 3%. The optimum side stream had a similar permeable water flux equivalent to the function of nine spacers with the equilateral triangle but with a lower amount of shear stress (1/2) and pressure drop (1/4). Likewise, an average water flux equivalent to an increase of 2.5 was created using a side stream and 3.5 times with an optimum spacer in the inlet flow velocity of the draw solution. A comparison of energy consumption showed that the side stream consumed less energy than the spacers and could improve process costs.

Investigation of Shear Mechanical Behavior and Slip Weakening Characteristics of Rough Joints in Rock Mass

The surface morphology of a structural plane is an important factor affecting the shear mechanical behavior of a structural plane. A direct shear test of a rough structural plane is carried out, and the shear mechanical behavior and slip weakening characteristics of a structural plane under different levels of roughness and normal stress conditions are studied; the normal stress conditions ranged from 2 MPa to 14 MPa. The results show that the shear strength and shear stress drop of a rough structure increase as the normal stress and roughness levels also increase. The higher the roughness level, or the greater the normal stress level, the more elastic energy the structural plane accumulates before shear failure. Once the shear stress is great enough and shear failure occurs, the shear slip of the rough structural plane shows obvious stick slip characteristics, and it releases more energy. Under high normal stress conditions, the convex body of the structural plane is damaged earlier in the process of direct shear, and the duration of convex body damage and failure is longer. After direct shear, the roughness of the structural plane decreases exponentially as normal stress levels increase. The shear slip of the structural plane, which has a significant degree of roughness under high normal stress conditions, shows a significant number of slip weakening characteristics, which is the main reason that the stick slip of the structural plane releases a lot of energy.

Slip transition of rock fractures due to chemical corrosion

Chemical corrosion of rock masses commonly exists in natural environment (e.g., rock masses immersed in acidic groundwater) and in rock engineering practice (e.g., acid fluid injection in unconventional reservoirs). Rock fractures as the primary paths for fluid flow are susceptible to the chemical treatment, which may lead to geologic hazards (e.g., induced landslides and earthquakes). Here we show the transitional behaviors of rock fractures between stick-slip and stable sliding due to the chemical corrosion, which is characterized by a sequence of fast rupture followed by one or more slow ruptures. The chemical corrosion also modifies the frictional properties of rock fractures, in terms of friction rate parameters, characteristic weakening distance, stiffness ratio, and frictional property ratio. Our results indicate that the chemical corrosion essentially reduces the critical stiffness of the fracture and makes it approach the stiffness of the loading system, resulting in the occurrence of slip transition. The slip transition is strongly influenced by treatment duration and shear process, and the real area of contact density is a physical control linking fracture surface topography and frictional responses, such as AE energy and shear stress drop. The understanding of slip transition can improve our ability to interpret the seismic data and to predict the slip behaviors.

Effects of near-fault stress evolution and surface asperities on rough fault slip: An evaluation based on photoelastic shear tests and additively printed models

Fault slip due to resource excavation activities is a potential cause of earthquakes and rockbursts; its fundamental cause is the redistribution of the near-fault stress field. Knowledge of the distribution and evolution of full-field stress around natural faults is crucial to revealing the mechanisms of fault slip. However, natural faults are rough and numerous asperities on their surfaces lead to stress heterogeneity, which makes quantifying the distribution and evolution of near-fault stress challenging. In this study, we explored the distribution and evolution of full-field stress in rough faults using photoelastic analyses of direct shear tests involving three-dimensional printed fault models. The near-fault shear stress and secondary principal stress difference (SPSD) in the printed fault models under various shear loads were quantified, the distribution and evolution characteristics of near-fault stresses were analyzed, and the influences of asperities on near-fault stress evolution were addressed. Our findings indicate that numerous stress concentrations form near the upslope segments of asperities during fault slip. Near-fault shear stress and SPSD present a high similarity in concentrated stress distribution and evolution. It is more effective to characterize the effect of surface asperities on the slip of rough faults using SPSD drops than using shear stress drops. The sequence of local SPSD drops is closely related to the area enveloped by uphill fault slope curves, which facilitates the prediction of earthquake nucleation. Our study provides a basis for characterizing the effects of near-fault stress and surface asperities on the slip of natural rough faults.

Physics‐Based Model Reconciles Caldera Collapse Induced Static and Dynamic Ground Motion: Application to Kīlauea 2018

AbstractInflationary deformation and very long period (VLP) earthquakes frequently accompany basaltic caldera collapses, yet current interpretations do not reflect physically consistent mechanisms. We present a lumped parameter model accounting for caldera block/magma momentum change, magma chamber pressurization, and ring fault (assumed vertical) shear stress drop. Pressurization of the underlying magma chamber is represented by a tri‐axial expansion source, and the combined caldera block/magma momentum change by a vertical single force. The model is applied to Kīlauea 2018 caldera collapse events, accurately predicting near field static/dynamic ground motions. In addition to the tri‐axial expansion source, the single force contributes significantly to the VLP waveforms. For an average collapse event with fully developed ring fault, Bayesian inversion constrains ring fault stress drop to ∼0.4 MPa and the pressure increase to ∼1.9 MPa. That the predictions fit both geodetic and seismic observations confirms that the model captures the dominant caldera collapse mechanisms.