Source Of Deformation Research Articles

Raw Gangue Filling Mining under Construction <br/>—A Case Study in China

In order to recover the strip pillar coal resources, reduce the amount of gangue mountain and realize remediation of the goaf environment in the old mining area, the raw gangue filling mining technology was proposed. According to the previous practical experience, the feasibility of the implementation of raw gangue filling mining technology in the coal-pressed area was analyzed. Through the filling gangue compaction test, the deformation under different loading stages was obtained. Further, a reasonable prediction of the deformation beyond the experimental limited loading load was made based on the experimental results. Through the deformation source analysis of the whole process of gangue filling, the key factors for controlling deformation before, during, and after filling were determined. Additionally, the proportion of deformation during different stages was quantified. Considering the protection of surface buildings, mining fullness of the working face and mining technology, the production parameters of 1209 and 1210 filling working faces were preliminarily determined. Through numerical simulation, the rationality of mining scheme was verified. Based on the practice of 1209 working face and the key factors to control the deformation of gangue filling, the mining system and process in 1210 working face were optimized. According to the measured surface rock movement, raw gangue filling mining technology can meet the requirements of surface building protection level. Especially, this paper provides a method to quantitatively calculate the equivalent mining height (EMH) of raw gangue filling and its mining deformation, which has reference significance for old mining areas.

DEM study on the macro- and micromechanical behaviours of breakable granular materials under cyclic loading

The effect of cyclic loading on the macro- and micromechanical behaviours of breakable granular materials was investigated via DEM. Breakable particle models composed of Voronoi cells with realistic shapes were constructed. A series of confined cyclic loading tests were performed at different loading amplitudes. The macroscopic deformation behaviours were investigated in terms of the cumulative plastic strain and dynamic resilience modulus. Then, particle breakage characteristics, including the extent of particle breakage, crack orientation distribution, breakage pattern and correlation between the particle breakage and energy input, were explored. Furthermore, micromechanical results, including the coordination number, sliding contact and contact orientation anisotropy, were examined. It is found that both particle breakage and cumulative plastic strain increase rapidly in the early stage of loading. In the stable state, both showed an S-shaped increase with increasing loading amplitude. This study highlights that particle breakage is one of the main sources of permanent deformation.

Plume-induced flood basalts on Hesperian Mars: An investigation of Hesperia Planum

Hesperian Mars was characterized by a unique style of geodynamic activity that left crucial volcano-tectonic records in the form of extensive flood lavas covered by wrinkle ridges. Yet, little is known about the context of their formation. Here, we perform a tectonic and geophysical investigation of Hesperia Planum, a 1700-km-diameter volcanic plain covered by wrinkle ridges. Our tectonic analysis reveals that the planum has the highest density of wrinkle ridges on the planet and a characteristic compressional peak strain of about 3.20 × 10−3, almost 2 times larger than typical Hesperian compressional strains. We invert gravity and topography data and find that simple crustal loading and volcanism cannot explain the tectonic record. An additional source of deformation is thus required. We demonstrate that a loading sequence of plume-induced uplift, volcanism, and subsidence, following an evolutionary path similar to flood basalt provinces on Earth better fits the observations. This plume model is able to explain the peak strain, crustal thinning, and low relief of Hesperia Planum. The inferred plume head size (∼1400 km) and temperature anomaly (∼320 K) are consistent with large terrestrial plumes. Based on a fit to the tectonic record, we determine a plume center location that correlates with a cluster of wrinkle ridges, local crustal thinning, and a circular magnetic low, where the latter could be the result of a thermal demagnetization of the lithosphere in the presence of the ascending plume. Our analysis suggests that scattered mantle plumes could be at the origin of Hesperia Planum and other late Noachian to early Hesperian volcanic provinces within the highlands.

Multiscale modelling and simulation of subsurface carbide deformation during the formation of white etching areas

One of the main failure indications in rolling bearings subjected to rolling contact fatigue (RCF) is premature subsurface cracking accompanied by white etching areas (WEAs). The cracks that are linked with WEAs are called white etching cracks (WECs). The formation mechanisms of WEAs/WECs are still highly debatable according to international state of art. Often SAE 52100 steel is used for bearing rings. Its microstructure consists of a martensitic or bainitic matrix and homogeneously distributed chromium rich cementite precipitations. There are two main hypotheses based on what forms first, the cracks or WEAs (hypothesis 1 & 2 respectively). There are many numerical studies that examine non-metallic inclusions as a source of cracks that leads to WEAs (hypothesis 1), but none that considers carbides as the source of severe plastic deformation subjected to RCF that leads to WEAs and, eventually WECs (hypothesis 2). In this study, the testing was conducted on a ZF-type modified RCF test rig with hydrogen charged samples to reproduce WEAs/WECs formation. Later the influence of the microstructural features of the carbides on the steel matrix, during the formation of WEAs was investigated by microstructural investigations and multiscale finite element modelling. It was found that carbides can contribute to severe local plastic deformation which leads to formation of WEAs. Thus, it also supported the likelihood of hypothesis 2. Additionally, the surface traction and microstructural characteristics of carbides are correlated with the wide range of WEAs formation depths and timescales.

Automated classification of A-DInSAR-based ground deformation by using random forest

ABSTRACT Wide-area ground motion monitoring is nowadays achievable via advanced Differential Interferometry SAR (A-DInSAR) techniques which benefit from the availability of large sets of Copernicus Sentinel-1 images. However, it is of primary importance to implement automated solutions aimed at performing integrated analysis of large amounts of interferometric data. To effectively detect high-displacement areas and classify ground motion sources, here we explore the feasibility of a machine learning-based approach. This is achieved by applying the random forest (RF) technique to large-scale deformation maps spanning 2015–2018. Focusing on the northern part of Italy, we train the model to identify landslide, subsidence, and mining-related ground motion with which to construct a balanced training dataset. The presence of noisy signals and other sources of deformation is also tackled within the model construction. The proposed approach relies on the use of explanatory variables extracted from the A-DInSAR datasets and from freely accessible informative layers such as Digital Elevation Model (DEM), land cover maps, and geohazard inventories. In general, the model performance is very promising as we achieved an overall accuracy of 0.97, a true positive rate of 0.94 and an F1-Score of 0.93. The obtained outcomes demonstrate that such transferable and automated approach may constitute an asset for stakeholders in the framework of geohazards risk management.

Development of extended STZ model for granular soils subjected to combined static loading and vibration

The ‘shear-transformation zone’ (STZ), which may be referred to as a weak domain in granular material, is the main source of plastic deformations in non-cohesive soils such as sand or gravel. To theoretically investigate the vibration-induced shear resistance reduction (ViSRR) of granular materials, in this paper an extended STZ model is proposed that considers the coupling effect between vibration and quasi-static loadings. The framework of the model consists of three components: (a) the motion of STZs including the transition, creation and destruction of STZs; (b) the relation between the motion of small-scale STZs and the observable, macroscopic plastic strain; and (c) the evolution law of a ‘configurational temperature’ that reflects the energy that drives the motion of STZs. The conventional STZ model developed for amorphous materials is enhanced to accommodate both volumetric and shear deformations in the spatial stress state. Specifically, in addition to considering plastic shear strains induced by the change in STZ orientation as the result of the transition, as in conventional STZ models, the extended STZ model correlates plastic volumetric strains with the change in STZ amount resulted from creation and destruction.

Transcrustal Compressible Fluid Flow Explains the Altiplano‐Puna Gravity and Deformation Anomalies

AbstractEnigmatic large‐scale (>150 km wide) ground deformation in southern Bolivia has been ongoing for more than 50 year. Concurrent changes in gravity recorded between 2010 and 2018 imply minor changes in subsurface density in the absence of significant mass changes. Numerical modeling of the gravity changes and concurrent InSAR LOS displacements gives annual bulk density changes of 0.002 kg m−3 in the Altiplano‐Puna Magma Body (APMB) and −0.03 kg m−3 in a vertical bulge‐column ensemble beneath Uturuncu volcano. We propose that the transcrustal migration of fluids from the APMB to shallower crustal levels by compressible flow is the source of ground deformation. Localized ground subsidence south of Uturuncu can be best explained by a density decrease of 20 ± 5 kg m−3 between 2011 and 2013 in a hydrothermal reservoir. Our findings contribute to the growing recognition of transcrustal fluid migration as a source of volcanic unrest.

Volcanic and Seismic Source Modeling: An Open Tool for Geodetic Data Modeling

Volcanic and Seismic source Modeling (VSM) is an open-source Python tool to model ground deformation. VSM allows the user to choose one or more deformation sources of various shapes as a forward model among sphere, spheroid, ellipsoid, rectangular dislocation, and sill. It supports multiple datasets from most satellite and terrestrial geodetic techniques: Interferometric SAR, GNSS, leveling, Electronic Distance Measurements, tiltmeters, and strainmeters. Two sampling algorithms are available: one is a global optimization algorithm based on the Voronoi cells and yields the best-fitting solution and the second follows a probabilistic approach to parameters estimation based on the Bayes theorem and the Markov chain Monte Carlo method. VSM can be executed as Python script, in Jupyter Notebook environments, or by its Graphical User Interface. Its broad applications range from high-level research to teaching, from single studies to near real-time hazard estimates. Potential users range from early-career scientists to experts. It is freely available on GitHub (https://github.com/EliTras/VSM) and is accompanied by step-by-step documentation in Jupyter Notebooks. This study presents the functionalities of VSM and test cases to describe its use and comparisons among possible settings.

Deformation induced by distributions of single forces in a layered half-space: [formula omitted

In the present paper we introduce a numerical model for the representation of displacement, strain and stress due to single forces embedded in a layered elastic half-space. The code EFGRN/EFCMP (Elastic Forces GReeN functions/Elastic Forces CoMPutation) is able to represent the mechanical effects due to pre-assigned distributions of single forces. Even if internal deformation sources can be described by distributions of equivalent body forces with vanishing resultant and moment, single forces are employed in geophysics to represent hydraulic and/or lithostatic loads, effects of internal density anomalies, and even some kind of seismic events. A distribution of single forces is also used to describe the effects of an inelastic inclusion located inside an elastic medium. In fact, the recent literature shows that poro-elastic and thermo-elastic inclusions can be represented using single forces distributed on their boundaries. EFGRN/EFCMP shares the benefits of rapid and semi-analytical calculation offered by the parent code, EDGRN/EDCMP, which is instead suitable for the representation of extended dislocation sources, as seismic faults. The present code also provides an option for computing the effects of a distribution of single forces embedded in a homogeneous half-space, by using the analytical solutions of Mindlin. Accordingly, EFGRN/EFCMP can be a valid support both for the representation of forward models of deformation sources and for the procedures of inversion of geodetic data in a layered medium. We show some applications of the code and we provide several scripts in MATLAB language which help the user to quickly start using EFGRN/EFCMP.

Modeling the Deformation Sources in Volcanic Environments Through Multi-Scale Analysis of DInSAR Measurements

In this work, we propose a multi-scale approach for modeling the ground deformation field of volcanic sources. The methodology is based on the use of Multiridge and ScalFun methods to analyze the elastic deformation fields by providing source information, such as the depth, the horizontal position, and its morphological features. This strategy is alternative with respect to the classical inverse approaches since it allows overcoming some aspects of the ambiguities related to the interpretation of DInSAR measurements. Indeed, the multi-scale method does not need a priori constraints on the model parameters to achieve an unambiguous solution. First, we argue on the general physical conditions so that the deformation field, generally represented by biharmonic functions, also satisfies Laplace’s equation and the law of homogeneity. This occurs in the case of sources with hydrostatic pressure-change embedded in an elastic half-space. In these conditions, the properties of harmonic and homogeneous functions can be employed to model the ground deformation fields using multi-scale procedures. Then, we demonstrate the soundness of the proposed approach through the application of Multiridge and ScalFun methods to synthetic tests. We analyze the fields generated by spherical, pipes- and sills-like sources and consider different model settings, as the layered half-space, the noisy, and the multi-source scenarios. For all these simulations, we achieve unconstrained information related to the source geometry with satisfying accuracy. Finally, in order to show the flexibility of the multi-scale approach in different volcanic environments, we use Multiridge and ScalFun methods for analyzing DInSAR measurements relevant to Uturuncu, Okmok, and Fernandina volcanoes, retrieving information about their volcanic systems. In the first case, we point out a transient source at a depth of 4.5 km b.s.l., which is activated during 2006–2007 together with the stable and well-known Altiplano Puna Magma Body (APMB); in the second one, we retrieve a concentrated body at a depth of 3.1 km b.s.l. during 2003–2004; and in the last case, we interpret the 2013 unrest episode as caused by a pipe-like source located at a depth of 1.7 km b.s.l.

Cyclical geothermal unrest as a precursor to Iceland’s 2021 Fagradalsfjall eruption

Understanding and constraining the source of geodetic deformation in volcanic areas is an important component of hazard assessment. Here, we analyse deformation and seismicity for one year before the March 2021 Fagradalsfjall eruption in Iceland. We generate a high-resolution catalogue of 39,500 earthquakes using optical cable recordings and develop a poroelastic model to describe three pre-eruptional uplift and subsidence cycles at the Svartsengi geothermal field, 8 km west of the eruption site. We find the observed deformation is best explained by cyclic intrusions into a permeable aquifer by a fluid injected at 4 km depth below the geothermal field, with a total volume of 0.11 ± 0.05 km3 and a density of 850 ± 350 kg m–3. We therefore suggest that ingression of magmatic CO2 can explain the geodetic, gravity and seismic data, although some contribution of magma cannot be excluded. Ingression of magmatic gas into a geothermal aquifer generated cyclical deformation and primed the system for the 2021 Fagradalsfjall eruption, Iceland, according to a catalogue of 39,500 precursory earthquakes combined with a poroelastic model.

Analytical Solutions for Gravity Changes Caused by Triaxial Volumetric Sources

AbstractVolcanic crises are often associated with magmatic intrusions or the pressurization of magma chambers of various shapes. These volumetric sources deform the country rocks, changing their density, and cause surface uplift. Both the net mass of intruding magmatic fluids and these deformation effects contribute to surface gravity changes. Thus, to estimate the intrusion mass from gravity changes, the deformation effects must be accounted for. We develop analytical solutions and computer codes for the gravity changes caused by triaxial sources of expansion. This establishes coupled solutions for joint inversions of deformation and gravity changes. Such inversions can constrain both the intrusion mass and the deformation source parameters more accurately.

Influence of Filament Winding Tension on the Deformation of Composite Flywheel Rotors with H-Shaped Hubs.

The residual stress plays an important role in composite flywheel rotors composed of filament windings. The fiber tension during high-prestressed winding is the main source of the rotor deformation and residual stress of composite layers. In this study, the effect of the winding tension gradient on deformation was monitored in real-time. Two types of in-plane winding tension fluctuation methods were developed to investigate the effect of tension on deformation. Online and offline measurements were performed for the strain acquisition. A wireless strain instrument was used for online deformation monitoring and a laser scanner was used for the offline surface reconstruction. Additionally, different filament winding strategies were carried out to improve the efficiency of the winding tension by finite element analysis. The results indicated that the deviation between numerical and experimental results was within 8%. Based on the proposed numerical method, the influence of the in-plane and out-of-plane winding tension gradient distributions on the rotation process of the H-shaped rotor was analyzed. An in-plane winding strategy with variable tension was developed, which increased the initial failure speed by 160%.

Mechanism of underexcavation and practical design method for building rectification

This study presents the mechanism of underexcavation and practical design method for building rectification. Underexcavation is widely used to restore for not only historic monuments but also modern steel–concrete buildings that undergo large differential settlement. Due to the lack of systematic theoretical research and design specifications, the rectification process mainly depends on real-time monitoring. To meet the urgent need to address building tilt whether caused by design errors or by environmental changes, a plane strain numerical simulation is introduced to probe the mechanism of underexcavation for building rectification. The whole process of soil failure and deformation during underexcavation have been analysed with a series of numerical models, and a simplified analysis method has been proposed for predicting key parameters for the design of a building rectification. The simulation results of a single-hole excavation demonstrate the features of soil stress redistribution, the character of the displacement field, the modes of soil failure and the expansion characteristics of the failure zone. The results of simulations of multi-hole underexcavation show the relationship between plastic failure around the holes and global failure of the shallow foundation and indicate that hole closure is the main source of deformation during rectification. Based on the numerical simulation results combined with engineering experience, two key parameters of optimum spacing and hole diameter are obtained.

New Insights Into the Recent Magma Dynamics Under Campi Flegrei Caldera (Italy) From Petrological and Geochemical Evidence

AbstractThe Campi Flegrei caldera is considered the most dangerous volcano in Europe and is currently in a new phase of unrest (started in 2000 and still ongoing) that has persisted intermittently for several decades (main crisis occurred from 1950 to 1952, 1970–1972, and 1982–1984). Here, by combining the petrological and geochemical data collected in recent decades with numerical simulations, we place new constraints on the source(s) of the current dynamics of the volcano. In particular, we show that the measured (N2‐He‐CO2) geochemical changes at the fumaroles of Solfatara hydrothermal site are the result of massive (about 3 km3) magma degassing in the deep portion (≥200 MPa, 8 km of depth) of the plumbing system. This degassing mechanism would be able to flood the overlying hydrothermal system with hot gas, thus heating and fracturing the upper crust inducing shallow seismicity and deformation. This implies that the deep magma transfer process (≥8 km) has been decoupled from the source of deformation and seismicity, localized in the first kilometers (0–4 km) of caldera‐filling rocks. This information on magma transfer depth can have important implications for defining the best monitoring strategies and for forecasting a future eruption. Finally, this study highlights how petrological and geochemical data allow us to explore the dynamics of the deep portion of the plumbing system and thus trace the occurrence of recharge episodes, in a portion of the ductile lower crust where magma transfer occurs in the absence of earthquakes.

Short-Range Millimeter-Wave Imaging in the Presence of Array Element Position Deviation

The focusing performance of an active short-range millimeter-wave imager is vulnerable to phase errors. As two major sources of phase error, delay uncertainty and array deformation are entangled when they are treated by conventional calibration methods, leading to defocusing. First, the defocusing effect caused by the array element position deviation (EPD) is graphically described in the form of ellipse deformation, indicating that the results of imaging a point target can inform on the distribution of EPD. Second, we analyze the phase error coupling problem to show that the EPD-caused phase error is spatially variant, therefore making the imaging performance sensitive to target location to varying extents bounded by the reference target location. Finally, a time-domain calibration method based on a constrained differential delay test is proposed to jointly mitigate the phase errors caused by both delay uncertainty and EPD. Numerical and experimental results demonstrate the efficacy of the proposed method.

Joint Inversion of GNSS and GRACE for Terrestrial Water Storage Change in California.

Global Navigation Satellite System (GNSS) vertical displacements measuring the elastic response of Earth's crust to changes in hydrologic mass have been used to produce terrestrial water storage change (∆TWS) estimates for studying both annual ∆TWS as well as multi‐year trends. However, these estimates require a high observation station density and minimal contamination by nonhydrologic deformation sources. The Gravity Recovery and Climate Experiment (GRACE) is another satellite‐based measurement system that can be used to measure regional TWS fluctuations. The satellites provide highly accurate ∆TWS estimates with global coverage but have a low spatial resolution of ∼400 km. Here, we put forward the mathematical framework for a joint inversion of GNSS vertical displacement time series with GRACE ∆TWS to produce more accurate spatiotemporal maps of ∆TWS, accounting for the observation errors, data gaps, and nonhydrologic signals. We aim to utilize the regional sensitivity to ∆TWS provided by GRACE mascon solutions with higher spatial resolution provided by GNSS observations. Our approach utilizes a continuous wavelet transform to decompose signals into their building blocks and separately invert for long‐term and short‐term mass variations. This allows us to preserve trends, annual, interannual, and multi‐year changes in TWS that were previously challenging to capture by satellite‐based measurement systems or hydrological models, alone. We focus our study in California, USA, which has a dense GNSS network and where recurrent, intense droughts put pressure on freshwater supplies. We highlight the advantages of our joint inversion results for a tectonically active study region by comparing them against inversion results that use only GNSS vertical deformation as well as with maps of ∆TWS from hydrological models and other GRACE solutions. We find that our joint inversion framework results in a solution that is regionally consistent with the GRACE ∆TWS solutions at different temporal scales but has an increased spatial resolution that allows us to differentiate between regions of high and low mass change better than using GRACE alone.

Variable inflation rate of a magmatic deformation source beneath Aira caldera after the 1914 eruption of Sakurajima volcano: Inferences from a linear Maxwell viscoelastic model constrained by geodetic data

Temporal variation of ground surface displacement rates at volcanoes may represent changes to the volumetric magma supply rate over time. If crustal rock responds elastically to a magmatic deformation source, the volume change of the source has a simple one-to-one relation to the surface deformation. For viscoelastic crustal rock, however, the correlation is not always straightforward, particularly at volcanoes where crustal viscosity is lowered by a high geothermal gradient. For a continuous inflation of the deformation source, the viscoelastic surface displacement depends on the balance between the uplift due to magma supply and subsidence due to viscoelastic relaxation. In this study, using a 3D finite element model composed of an elastic layer underlain by a linear Maxwell viscoelastic layer with a spatially uniform viscosity, we estimate the temporal variation of volumetric magma supply rate into the upper crust beneath Aira caldera in southern Kyushu, Japan, after the 1914 eruption of Sakurajima volcano. It is found that the geodetic data, including levelling and GNSS displacement fields, require a sill-like magmatic deformation source at a depth of 11 km to inflate at the following rates for six different periods: (I) ~6.9–9.4 × 106 m3/yr in 1914–1934, (II) ~9.1–16.7 × 106 m3/yr in 1934–1960, (III) ~1.6–3.8 × 106 m3/yr in 1960–1968, (IV) ~8.1–11.0 × 106 m3/yr in 1968–1976, (V) ~ −1.0–2.2 × 106 m3/yr in 1976–1997, and (VI) ~5.8–9.4 × 106 m3/yr in 1997–2007. The constrained viscosity (ηc) of the viscoelastic crust ranges from ~5 × 1018 Pa s to ~1020 Pa s or more. The lowest and highest values produce the best fit to the data in the earliest period and in period V showing surface subsidence, respectively, but for the other periods any viscosity is acceptable unless it is lower than ~1018 Pa s. The lowest viscosity providing the best fit in the earliest period indicates that viscoelastic displacement in response to the 1914 eruption plays an important role in the surface deformation field. The observed surface subsidence in period V can be explained either by inflation or deflation of the deformation source, depending on whether ηc is lower or higher than ~1019 Pa s, respectively. The subsequent surface recovery in period VI requires an increase in the inflation rate for any case of ηc. The volume of magma accumulated since the 1914 eruption (ΔV) is predicted to be ~0.6–0.8 km3 in 2020. The estimated inflation/deflation rate of the deformation source, in comparison with the observed volumetric eruption rate, reveals that a significant eruption occurs only when ΔV is ~0.4 km3 or more. However, even if ΔV is beyond the critical value, the eruptive activity does not depend on ΔV. The temporal inflation rate inferred in this study gives an opportunity to discuss eruptive dynamics in relation to the observed eruptive activity, such as a quantitative relationship between magma supply rate into, and discharge rate from, a deformation source.

A multiscale indentation-based technique to correlate acoustic emission with deformation mechanisms in complex alloys

Conventional methodologies to link damage evolution with the activation of deformation mechanisms typically require destructive testing and post-mortem analysis. More recently, mechanical testing combined with acoustic emission analysis has provided a method to fingerprint multiple active deformation mechanisms. However, correlating different acoustic emission signals with active deformation sources remains a non-trivial task due to the simultaneous activation of sources during mechanical testing. Here, we demonstrate a multiscale indentation-based technique to isolate dislocation and martensitic transformation sources in the acoustic emission data of a complex alloy. For this purpose, the acoustic emission signals from macro- and microindentation experiments are compared with microscopy and crystallographic analysis of deformed microstructures. A key feature of this method is the selective activation of the martensitic transformation during microindentation, which enables separate fingerprinting of this deformation mechanism. An unsupervised k mean clustering methodology is leveraged to classify acoustic emission waveforms into clusters, which facilitates the detection of shared deformation mechanisms across different tests. The results of this study provide a rapid non-destructive tool to correlate acoustic emission sources with deformation mechanisms in complex alloys.

Geodetic Constraints on a 25‐year Magmatic Inflation Episode Near Three Sisters, Central Oregon

AbstractCrustal inflation near the Three Sisters volcanic center documented since the mid‐1990s has persisted for more than two decades. We update past analyses of the event through 2020 by simultaneously inverting InSAR interferograms, GPS time series, and leveling data for time‐dependent volcanic deformation source parameters. We explore several source models to estimate how the deformation rate varied through time and to identify parameters that can reproduce measured deformation. Our preferred model is a Mogi source 4.1 km below sea level (5.9 km below the surface) about 5 km west of the summit of South Sister. Inflation started in late 1995 or 1996; the rate increased rapidly during 1998–1999, and peaked in late 1999, resulting in maximum surface uplift of about 30 cm by mid‐2020. Since 2000, the inflation rate generally declined exponentially with a time constant of about 6 years. Two source inflation scenarios fit the data equally well. In the first, the crust surrounding the source is elastic and the net source‐volume increase, which we attribute to persistent magma input, has been about 49 × 106 m3. The second scenario adds a viscoelastic shell surrounding the Mogi source. In that case, an injection of about 21 × 106 m3 of magma prior to 2000, followed by continuing relaxation of the viscoelastic shell, can account for most of the observed surface deformation. In both scenarios, modeling reveals quasiperiodic increases in the inflation rate (pulses) with a recurrence interval of 3–4 years, both before and after 2000.