Accumulation Of Slip Research Articles

Improving the fatigue property of diffusive film cooling holes in nickel-based single crystal superalloy via ultrashort pulse laser drilling coupled with abrasive flow machining

A novel hole-making technique, which combines ultrashort pulse (UP) laser drilling with abrasive flow machining (AFM), has been developed to enhance the surface quality and fatigue resistance of diffusive holes in nickel-based single crystal (NBSC) superalloys. This study conducted a comprehensive analysis of the surface morphology and metallurgical characteristics of the hole wall, evaluated by fatigue testing at elevated temperatures and fractography analysis. The findings demonstrate that AFM can effectively eliminate the solidified debris generated during UP laser drilling, significantly reducing surface roughness and inducing a rounded effect at the outlet acute zone of the diffusive hole. Such improvements have been shown to increase the fatigue life of the holes by up to 50.6 % compared to those without polish. Furthermore, the crystal plasticity finite element method (CPFEM) was employed to investigate the localized stress concentration and the accumulation of plastic slip around the diffusive hole, elucidating the mechanisms behind fatigue failure in NBSC superalloys. The study also discusses the influence of the different hole-making technology on the fatigue properties of diffusive holes, integrating CPFEM results with analyses of surface quality and fatigue fractography. The study conducted in this study can provide valuable guidance for the fabrication of diffusive holes in turbine blades. Furthermore, it can also improve our understanding of the fatigue failure mechanism of diffusive holes in NBSC superalloy.

MHD hybrid nanofluid and slip flow towards an exponentially stretching/shrinking sheet with nonlinear thermal radiation and nonuniform heat source/sink

The analysis of heat transfer of a hybrid nanofluid [Formula: see text] in the MHD stagnation point motion toward an exponentially expanding/shrinking sheet with a nonuniform heat source/sink, multiple slip conditions and nonlinear thermal radiation effects are carried out in this study. By applying the similarity transformation, the governing equations are transformed into Ordinary Differential Equations (ODEs). The Runge–Kutta method using bvp4c in MATLAB software is implemented to explain the ODEs. The results show that the local Nusselt number is decreased while the skin friction coefficient remains unaltered by the accumulation of thermal slip, space, and temperature-dependent parameters.

The effect of anisotropic rate dependency on the deformation response of Ti-6242 during dwell fatigue loading

The α phase of titanium alloys is known to exhibit both elastic and plastic anisotropic mechanical behavior during deformation loading. Recent experimental studies indicate that single crystal rate dependency may also be anisotropic, though these studies are limited in scale and scope. Consequently, we present a study in which anisotropic rate dependency is studied on polycrystalline samples via crystal plasticity finite element (CPFE) simulations, which are compared against previously-published data from electron backscatter diffraction/digital image correlation (EBSD-DIC) experiments. Cold dwell fatigue loading is utilized, owing to the propensity for transient behavior during constant-load dwells, which is hypothesized to be sensitive to the relative rate dependencies on different slip families (i.e., basal, prismatic, and pyramidal) in hexagonal close packed crystals. A suite of CPFE simulations is conducted on polycrystalline samples in which the slip family rate dependency values are parameterized. We analyze simulation results by focusing on the slip activity and accumulation of slip on the various slip families as a function of dwell cycles, as well as the transient effect during singular dwell cycles, for hundreds of crystals simultaneously. Results are further discussed through the lens of findings from EBSD-DIC experiments.

An Approach to Measure Slips in Friction Contacts Using a Self-Powered Sensor

The accumulation of small tangential slip will occur on the contact surfaces of components in mechanical structures when subjected to cyclic loadings, which will lead to system failure. However, the small tangential slip is difficult to measure directly. In this paper, a method for measuring the contact slip by using a self-powered displacement sensor based on triboelectric nanogenerator (TENG) is proposed, and the accuracy is verified by the finite element analysis (FEA). The contact slips for a flat-on-flat contact configuration are measured by this method. When the test piece is subjected to a cyclic tangential load with a frequency of 10Hz, the average obtained slip displacement of the test piece under single load cycle is less than 10μm. Then the finite element simulation of the contact configuration is carried out using software Abaqus 6.14. The analysis results are close to the test results, which verifies the effectiveness of the measurement method. Moreover, the slips of the flat-on-flat contact configuration under different frequency and amplitude of cyclic tangential load are investigated.

Crack mechanism correlated with Sn grain orientations on Ni metal surface subjected to 1000 thermal shocks

With the rapid development of 3D packaging, it is of great practical significance to understand the failure mechanism of solder joints in heterogeneous integration devices. In this study, the grain orientation and microstructure evolution of SAC305 solder joints were investigated in thermal shock tests for fan-out wafer level packaging. The heterogenous evolution of microstructure in Sn–3Ag-0.5Cu (SAC305) solder joints was investigated using electron backscattered diffraction (EBSD) and nanoindentation analysis. When the thermal shock reaches 1000 cycles, the local deformation caused the heterolattices in the joint to rotate toward the corners due to the thermal expansion. During deformation, sub-grain formation is accompanied by an increase in dislocations, the accumulation of plastic slip, and the activation of slip systems. The energy stored by this deformation is released in the form of cracks. The work in this paper provides new insights into the early stages of grain orientation, microstructural deformations and the accumulation of stored energy associated with these deformations, providing a scientific basis for the application and failure analysis of large size fan-out welded joints in complex working conditions.

A crystal plasticity approach to understand fatigue response with respect to pores in additive manufactured aluminium alloys

A crystal plasticity finite element modelling method integrated with a stored energy density criterion is utilized to comparatively investigate fatigue crack nucleation behaviour and quantify fatigue life with respect to different pore types in AlSi10Mg fabricated by selective laser melting. Representative microstructural models show that fatigue crack nucleation exhibits high sensitivity to both gas/keyhole and lack of fusion pores, but particularly the latter, which leads to much lower fatigue life at high stress levels. Multi-intragranular slip system activations occurring at the sharp corners of lack of fusion pores contribute to substantial increase in local geometrically necessary dislocation density. Together with the rapid accumulation of slip, these drive high local stored energy density at the tips of lack of fusion pores. For gas/keyhole pores, high stresses lead to pore-induced shear band formation which shifts the origin of crack nucleation away from the pore to other microstructural features. At low stresses, fatigue life for lack of fusion and gas/keyhole pores tend to converge but remain shorter than for pore-free microstructures.

Pre-control of annealing temperature on the uniformity of deformed structure of wrought magnesium alloy

Due to the accumulation of slip and twinning, the deformed structure of the wrought magnesium alloy is unevenly distributed, resulting in stress concentration, leading to its poor formability. Microstructure evolution in dense areas and sparse areas of deformed structure at different annealing temperatures are explored in this study, and the competitive relationship between the nucleation and growth of recrystallization at different temperatures and its influence on the uniformity of the structure are analyzed. Annealing temperature can improve the uniformity of the deformed structure of wrought magnesium alloys by affecting the sequence of recrystallization in dense areas of the deformed structure and grain growth in sparse areas of the deformed structure.

Throw-rate variations within linkage zones during the growth of normal faults: Case studies from the Western Volcanic Zone, Iceland

This work investigates how throw-rates vary within fault bends and sites of fault linkage during the process of normal fault growth. In the Western Volcanic Zone, Iceland, through detailed field mapping and field measurements of fault throws, normal faults are mapped and along-strike throw profiles are constructed in order to understand how the throw-rates relate with the local fault geometry along faults at different stages of linkage. The results show that throw-rates increase within linkage zones and propagating fault bends independently from the stage of maturity of the fault bend. This implies that 1) the relationship between the local fault geometry and the along-strike distribution of throw-rate is driven by the deeper part of the fault, where established fault bends start propagating to the surface; 2) faults grow first by linkage and coalescence of separate faults, and then by accumulation of slip on the resultant fault, in agreement with models of fault growth by linkage and coalescence; 3) incipient fault bends can produce uncertainty associated with palaeoseismological results, if fault bends remain unrecognised. Moreover, this work demonstrates that existing models showing increased co-seismic and throw-rates within fault bends and sites of fault linkage found in continental extensional settings are valid in a geodynamic context of a mid-oceanic rifts.

In-situ electron backscatter diffraction of thermal cycling in a single grain Cu/Sn-3Ag-0.5Cu/Cu solder joint

The heterogeneous evolution of microstructure in a single grain Cu/SAC305/Cu solder joint is investigated using in-situ thermal cycling combined with electron backscatter diffraction (EBSD). Local deformation due to thermal expansion mismatch results in heterogeneous lattice rotation within the joint, localised towards the corners. This deformation is induced by the constraint and the coefficient of thermal expansion (CTE) mismatch between the β-Sn, Cu6Sn5 and Cu at interfaces. The formation of subgrains with continuous increase in misorientation is revealed during deformation, implying the accumulation of plastic slip at the strain-localised regions and the activation of slip systems (110)[11]/2 and (0)[111]/2.

Extended ductility due to kink band formation and growth under tensile loading in single crystals of Mg-Zn-Y alloy with 18R-LPSO structure

The deformation behaviour of single crystals of an Mg85Zn6Y9 alloy with an 18R-LPSO structure was experimentally and numerically investigated using a micro-tensile testing method and a crystal plasticity finite element method, respectively. The deformation microstructure was characterised using optical and electron microscopy. The experimental results indicated that kink band was formed in the specimens depending on the initial crystal orientation relative to the loading direction. The kink banding was accompanied with remarkable ductility of over 50% nominal strain. The deformation behaviour observed was successfully reproduced in a crystal plasticity finite element analysis. The numerical results indicated that the kink band was formed by the accumulation of basal slip, which was enhanced by the geometrical softening owing to the lattice rotation. The growth of a kink band, which was reasonably explained by the changes in Schmid factor for a basal slip system due to lattice rotation, suppressed the localised failure at low strain. This resulted in the observed extended ductility, even in the LPSO structure with strong plastic anisotropy.

Cisplatin-loaded, Sialyl Lewis X-Modified Liposomes: Drug Release, Biodistribution and Antitumor Efficacy.

The aim of this study was to evaluate the characteristics of two cisplatin (CDDP)-loaded, sialyl Lewis X-modified liposomes (CDDP-SLX-LIP) with different particle size. Each had the same lipid composition and CDDP concentration, but a different drug-to-lipid ratio. The amount of platinum in the filtrates was determined by the ICP method. The antitumor effect was assessed using rats bearing MRMT-1 tumor. CDDP release was faster from the larger liposome formulation (L-LIP) than from the smaller one (S-LIP). Treatment with the two CDDP-SLX-LIPs resulted in comparable antitumor effects without obvious side-effects, but treatment with CDDP solution resulted in significant weight loss and an elevated BUN. Tumor accumulation of CDDP-SLX-LIP was clearly greater than that of CDDP solution and accumulation of S-LIP was greater than that of L-LIP. CDDP-SLX-LIP exhibited antitumor effects depending on their release behavior and tumor accumulation.

Prediction of ductile fracture induced by contraction twinning in AZ31 sheet subjected to uniaxial and biaxial stretching modes

The formability of AZ31 sheets was experimentally measured for uniaxial tension, plane strain stretching, and equi-biaxial stretching modes. The limit strain of the specimen was reasonable under uniaxial tension but was drastically reduced in the biaxial stretching modes. Full-field strain analysis and the observation of the fracture surface revealed that the specimen fractured without the formation of a visible local necking. To predict the fracture behavior using a crystal plasticity-based finite element method, a mean field model was developed to solve the mechanical interplay between the parent and twins. The destabilization of the specimen was simulated by introducing fracture criteria as functions of the accumulated slip inside the contraction twin region. Simulations revealed that strong strain heterogeneity forms in the case of the biaxial stretching modes, and this heterogeneity is apparently reduced under uniaxial tension as a result of the activation of prismatic slip, which produces a uniform strain distribution. Contraction twins nucleate at smaller strain levels in the biaxial stretching modes, and premature failure is predicted in the biaxial stretching modes as a result of the accumulation of slip in the twinned regions. Parametric studies show that even when the volume fraction of twins is small, they have a significant impact on the ductility of AZ31 sheets.

Afterslip Behavior following the 2014 M 6.0 South Napa Earthquake with Implications for Afterslip Forecasting on Other Seismogenic Faults

Research Article| March 23, 2016 Afterslip Behavior following the 2014 M 6.0 South Napa Earthquake with Implications for Afterslip Forecasting on Other Seismogenic Faults James J. Lienkaemper; James J. Lienkaemper aU.S. Geological Survey, MS 977, 345 Middlefield Road, Menlo Park, California 94025 U.S.A.jlienk@usgs.gov Search for other works by this author on: GSW Google Scholar Stephen B. DeLong; Stephen B. DeLong aU.S. Geological Survey, MS 977, 345 Middlefield Road, Menlo Park, California 94025 U.S.A.jlienk@usgs.gov Search for other works by this author on: GSW Google Scholar Carolyn J. Domrose; Carolyn J. Domrose bDepartment of Geosciences, San Francisco State University, 1600 Holloway Avenue, San Francisco, California 94132 U.S.A. Search for other works by this author on: GSW Google Scholar Carla M. Rosa Carla M. Rosa aU.S. Geological Survey, MS 977, 345 Middlefield Road, Menlo Park, California 94025 U.S.A.jlienk@usgs.gov Search for other works by this author on: GSW Google Scholar Author and Article Information James J. Lienkaemper aU.S. Geological Survey, MS 977, 345 Middlefield Road, Menlo Park, California 94025 U.S.A.jlienk@usgs.gov Stephen B. DeLong aU.S. Geological Survey, MS 977, 345 Middlefield Road, Menlo Park, California 94025 U.S.A.jlienk@usgs.gov Carolyn J. Domrose bDepartment of Geosciences, San Francisco State University, 1600 Holloway Avenue, San Francisco, California 94132 U.S.A. Carla M. Rosa aU.S. Geological Survey, MS 977, 345 Middlefield Road, Menlo Park, California 94025 U.S.A.jlienk@usgs.gov Publisher: Seismological Society of America First Online: 14 Jul 2017 Online Issn: 1938-2057 Print Issn: 0895-0695 © 2016 by the Seismological Society of America Seismological Research Letters (2016) 87 (3): 609–619. https://doi.org/10.1785/0220150262 Article history First Online: 14 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation James J. Lienkaemper, Stephen B. DeLong, Carolyn J. Domrose, Carla M. Rosa; Afterslip Behavior following the 2014 M 6.0 South Napa Earthquake with Implications for Afterslip Forecasting on Other Seismogenic Faults. Seismological Research Letters 2016;; 87 (3): 609–619. doi: https://doi.org/10.1785/0220150262 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search ABSTRACT The 24 August 2014 M 6.0 South Napa, California, earthquake exhibited unusually large slip for a California strike‐slip event of its size with a maximum coseismic surface slip of 40–50 cm in the north section of the 15‐km‐long rupture. Although only minor (<10 cm) surface slip occurred coseismically in the southern 9 km section of the rupture, considerable postseismic slip occurred, so that the maximum total slip one year after the event approached 40–50 cm, approximately equal to the coseismic maximum in the north. We measured the accumulation of postseismic surface slip on four ∼100‐m‐long alignment arrays for one year following the event. Because prolonged afterslip can delay reconstruction of fault‐damaged buildings and infrastructure, we analyzed its gradual decay to estimate when significant afterslip would likely end. This forecasting of Napa afterslip suggests how we might approach the scientific and engineering challenges of afterslip from a much larger M∼7 earthquake anticipated on the nearby urban Hayward fault. However, we expect its afterslip to last much longer than one year. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

On rate-dependent polycrystal deformation: the temperature sensitivity of cold dwell fatigue.

A temperature and rate-dependent crystal plasticity framework has been used to examine the temperature sensitivity of stress relaxation, creep and load shedding in model Ti-6Al polycrystal behaviour under dwell fatigue conditions. A temperature close to 120°C is found to lead to the strongest stress redistribution and load shedding, resulting from the coupling between crystallographic slip rate and slip system dislocation hardening. For temperatures in excess of about 230°C, grain-level load shedding from soft to hard grains diminishes because of the more rapid stress relaxation, leading ultimately to the diminution of the load shedding and hence, it is argued, the elimination of the dwell debit. Under conditions of cyclic stress dwell, at temperatures between 20°C and 230°C for which load shedding occurs, the rate-dependent accumulation of local slip by ratcheting is shown to lead to the progressive cycle-by-cycle redistribution of stress from soft to hard grains. This phenomenon is termed cyclic load shedding since it also depends on the material's creep response, but develops over and above the well-known dwell load shedding, thus providing an additional rationale for the incubation of facet nucleation.

Investigation of a new steel-concrete connection for composite bridges

A new type of connection for steel-concrete composite bridges was developed by the Steel Structures Laboratory of Ecole Poytechinque <TEX>$F{\acute{e}}d{\acute{e}}rale$</TEX> de Lausanne. Resistance to longitudinal shear is based on the development of shear stresses in the confined interfaces which form the connection. Confinement is provided by the reinforced concrete slab which encloses the connection and restrains the uplift (lateral separation) of the interfaces by developing normal stresses. The experimental investigation of the interfaces, under static and cyclic loading, enabled the development of the laws describing the structural behaviour of each interface. Those laws were presented by the authors in previous papers. The current paper focuses on the continuity of the research. It presents the experimental investigation on the new connection by means of push-out tests on specimens submitted to static and cyclic shear loading. Investigation revealed that the damage in the connection, due to cyclic loading, is expressed by the accumulation of a residual slip. A safe fatigue failure criterion is proposed for the connection which enabled the verification of the connection for the fatigue limit state with respect to the limit of fatigue. A numerical model is developed which takes into account the laws describing the interface behaviour and the analytical expressions for the confinement effect, the latter obtained by performing finite element analysis. This numerical model predicts the shear resistance of the connection and enables to assess its fatigue limit which is necessary for the fatigue design proposed.

Modeling the microstructure influence on fatigue life variability in structural steels

The endurance and HCF lifetime of multiphase steel components depend mainly on the phase of fatigue microcrack initiation and early propagation. A numerical study, which quantitatively describes the influence of microstructural features on the initiation and growth of cyclic microcracks, is presented within the context of microstructure-sensitive modeling. The implementation of kinematic hardening on each slip system in a crystal plasticity model allows for capturing the local accumulation of plastic microdeformation representing slip irreversibility occurring in the crack incubation phase. A load increasing testing technique with continuous temperature measurement and interrupted cyclic bending experiments deliver information about the endurance strength of a structural steel and allow for metallographic observation of cyclic microcrack propagation and thereby provide the experimental basis for the numerical simulations. The material model is implemented in cyclic computations with statistically representative volume elements, which are based on experimental microstructure description using the electron backscatter diffraction technique (EBSD). The extreme value distributions of the computed accumulation of local dislocation slip are then correlated to the microstructure in an approach to assess and explore the validity extent of microstructure-sensitive modeling using fatigue indicator parameters (FIPs) to correlate to the endurance limit and fatigue life under high-cycle fatigue conditions. The eligibility of consideration of the stresses normal to the planes of localized plastic damage assisting fatigue crack formation into these FIPs is investigated.

A geometric approach to modeling microstructurally small fatigue crack formation: III. Development of a semi-empirical model for nucleation

It has been observed during fatigue cracking of AA 7075-T651 that a small percentage of Al7Cu2Fe particles crack during manufacturing or very early in their life. Some of the cracked particles eventually nucleate cracks into the surrounding microstructure, and among these the number of cycles required for nucleation varies widely. It is important to comprehend the mechanics underpinning the observed variation so that the subsequent propagation stage can be accurately modeled. To this end, finite element models of replicated grain and particle geometry are used to compute mechanical fields near monitored cracked particles using an elastic–viscoplastic crystal plasticity model that captures the effect of the orientation of the grains near each monitored particle. Nonlocal, slip-based metrics are used to study the localization and cyclic accumulation of slip near the cracked particles providing mechanics-based insight into the actuation of the nucleation event. A high slip localization and cyclic accumulation rate are found to be a necessary, but not sufficient, condition for nucleation from cracked particles. A sufficient local driving stress must also be present, which is strongly dependent on the local microstructure and accumulated slip. Furthermore, the simulation results elucidate a quantitative relationship between the slip accumulated during fatigue loading and a consequential reduction of the critical local driving stress for nucleation, providing a physical basis for the fatigue damage concept. The observed nucleation direction is orthogonal to the computed local maximum tangential stress direction, as expected for this alloy. The main result is a semi-empirical model for the number of cycles required for nucleation, which is dependent on the maximum tangential stress and cyclic slip-accumulation rate near a cracked particle.

Coastal subsidence in Oregon, USA, during the giant Cascadia earthquake of AD 1700

Quantitative estimates of land-level change during the giant AD 1700 Cascadia earthquake along the Oregon coast are inferred from relative sea-level changes reconstructed from fossil foraminiferal assemblages preserved within the stratigraphic record. A transfer function, based upon a regional training set of modern sediment samples from Oregon estuaries, is calibrated to fossil assemblages in sequences of samples across buried peat-mud and peat-sand contacts marking the AD 1700 earthquake. Reconstructions of sample elevations with sample-specific errors estimate the amount of coastal subsidence during the earthquake at six sites along 400 km of coast. The elevation estimates are supported by lithological, carbon isotope, and faunal tidal zonation data. Coseismic subsidence at Nehalem River, Nestucca River, Salmon River, Alsea Bay, Siuslaw River and South Slough varies between 0.18 m and 0.85 m with errors between 0.18 m and 0.32 m. These subsidence estimates are more precise, consistent, and generally lower than previous semi-quantitative estimates. Following earlier comparisons of semi-quantitative subsidence estimates with elastic dislocation models of megathrust rupture during great earthquakes, our lower estimates for central and northern Oregon are consistent with modeled rates of strain accumulation and amounts of slip on the subduction megathrust, and thus, with a magnitude of 9 for the AD 1700 earthquake.

Along-strike growth of the Ostler fault, New Zealand: Consequences for drainage deflection above active thrusts

[1] Rarely are geologic records available to constrain the spatial and temporal evolution of thrust-fault growth as slip accumulates during repeated earthquake events. Here, we utilize multiple generations of dated and deformed fluvial terraces to explore two key aspects of the along-strike kinematic development of the Ostler fault zone in southern New Zealand over the past ∼100 k.y.: accumulation of fault slip through space and time and fixed-length thrust growth that results in patterns of drainage diversion suggestive of laterally propagating faults. Along the Ostler fault, surface deformation patterns revealed by topographic surveying of terrace profiles in nine transverse drainages define systematic variations in fault geometry and suggest deformation over both listric and planar thrust ramps. Kinematic modeling of folded terrace profiles and >100 fault-scarp surveys along major fault sections reveals remarkably similar slip distributions for multiple successions of geomorphic surfaces spanning ∼100 k.y. Spatially abrupt and temporally sustained displacement gradients across zones of fault section overlap suggest that either persistent barriers to fault propagation or interference between overlapping faults dominate the interactions of fault tips from the scale of individual scarps to the entire fault zone. Deformed terrace surfaces dated using optically stimulated luminescence and cosmogenic radionuclides indicate steady, maximum rates of fault slip of ∼1.9 mm/yr during the Late Quaternary. Slip data synthesized along the central Ostler fault zone imply that displacement accumulated at approximately constant fault lengths over the past ∼100 k.y. A northward temporal progression of abandoned wind gaps along this section thus reflects lateral tilting in response to amplification of displacement, rather than simple fault lengthening or lateral propagation. Oscillations of climate at ∼104-yr time scales modulate the formation and incision of geomorphic surfaces during successive glacial stages. Superimposed on apparently steadier rates of fault slip, such climate-dependent surfaces contribute to a pattern of progressive drainage deflection along the central Ostler fault zone that is largely independent of fault propagation.

Seismically and geodetically determined nondouble‐couple source mechanisms from the 2000 Miyakejima volcanic earthquake swarm

The volcanic eruption on Miyakejima, Japan, in 2000 was marked by the largest earthquake swarm ever recorded in Japan, a seismicity migration accompanying a dike intrusion as the dike propagated from Miyakejima to the northwest, and formation of a caldera on Mount Oyama on Miyakejima. In this study, we propose a seismic source model which can be used to model both seismic and geodetic displacements from volcanic earthquakes. Our model, the “crack + double‐couple” (CDC) model, combines tensile opening with shear slip along a single fault plane. We find that this model can fit both seismic and GPS data from the 1 July and 30 July earthquakes, the largest two in the Miyakejima sequence. The results of our GPS inversions for these two earthquakes are consistent with the seismic mechanisms and aftershock locations, and the GPS mechanisms successfully forward predict the observed regional seismograms. The 1 July earthquake, located near the northwest tip of the dike, has a large opening component and a geodetic moment about 5 times larger than that inferred from the seismic data alone. The source process for this event consists of tensile failure, which occurred quickly, and a much slower accumulation of shear slip. We apply the CDC model to 16 additional earthquakes from this sequence and find that the CDC model fits the seismic data for these earthquakes at least as well as established seismic moment tensor models.