Elastic Dislocation Model Research Articles

Potential Inundation Hazards in the Taipei Basin Induced by Reactivation of the Shanchiao Fault in Northern Taiwan

The Shanchiao fault, located to the west of the Taipei Basin in northern Taiwan, is a highly active normal fault that has a left-slip component and fault length of over 40 km. We suggest that the Shanchiao fault still has the ability to induce coseismic subsidence in the Taipei Basin under present extensional regime of northern Taiwan. In order to characterize the coseismic ground deformation and assess the potential inundation hazards in Taipei Basin, we estimate surface displacements using elastic dislocation models. The largest slip is assumed to be located underneath the Kuandu area due to the observation of deepest Tertiary basement in this area. Based on the topography changes due to coseismic deformation in a potential magnitude 7 event induced by reactivation of the Shanchiao fault, a 2D inundation model was adopted to simulate several inundation scenarios, including potential flood inundation below high tide condition and under various return-period design rainfall events. The predicted inundation maps based on various return-period flood events can provide information to assess potential earthquake-induced inundation hazards.

Study on crustal deformation of the Ms6. 6 Damxung earthquake in 2008 by InSAR measurements

Three Envisat images from ESA were used to derive the pre – and co-seismic deformation interfereograms caused by the Damxung Ms6. 6 earthquake of Oct. 6, 2008, by using InSAR. The result shows no significant crustal motion more than 4 months before the earthquake, but a maximum co-seismic displacement of about 0.3 m in an epicentral area of 20 km × 20 km. The deformation field was symmetrically distributed about a NS axis, where the west side subsided and the east side uplifted. We used a linear elastic dislocation model in half space and a nonlinear constraint optimized algorithm to estimate the slip distribution along the fault. The results indicates that the epicenter is located at 90.374°E, 29.745°N with a moment magnitude of Mw6. 35. The earthquake is dominated by normal faulting with a maximum slip of 3 m on a 12 km × 11 km fault plane striking S189°W, dipping 60° to NW at a depth of 9.5 km, and is located at a sub-fault of the southeastern Piedmont of the Nyainqentanglha mountains. The relatively shallow depth of earthquake is related to relatively high heat flow in the area.

Crustal deformation in northwestern Arabia from GPS measurements in Syria: Slow slip rate along the northern Dead Sea Fault

SUMMARY New Global Positioning System (GPS) measurements in NW Syria provide the first direct observations of near-field deformation associated with the northern Dead Sea fault system (DSFS) and demonstrate that the kinematics of the northern section of this transform plate boundary between the Arabian and Sinai plates deviate significantly from plate model predictions. Velocity estimates based on GPS survey campaigns in 2000, 2007 and 2008, demonstrate left-lateral shear along the northern DSFS with 1σ uncertainties less than 0.7 mm yr−1. These velocities are consistent with an elastic dislocation model with a slip rate of 1.8–3.3 mm yr−1 and a locking depth of 5–16 km. This geodetically determined slip rate is about half of that reported farther south along the central section (Lebanese restraining bend) and the southern section (Jordan Valley and Wadi Araba) of the transform and consequently requires some deformation to occur away from the transform along other geological structures. The factor of two difference in slip rates along the transform is also consistent with differing estimates of total fault slip that have occurred since the mid Miocene: 20–25 km along the northern DSFS (in NW Syria) versus about 45 km along the southern DSFS segment. Some of the strain deficit may be accommodated by north–south shortening within the southwestern segment of the Palmyride fold belt of central Syria. Additionally, a distinct change in velocity occurs within the Sinai plate itself. These new GPS measurements, when viewed alongside the palaeoseismic record and the modest level of present-day seismicity, suggest that the reported estimates of recurrence time of large earthquakes (M > 7) along the northern section of the DSFS may be underestimated owing to temporal clustering of such large historical earthquakes. Hence, a revised estimate of the earthquake hazard may be needed for NW Syria.

The 2005 Ilan earthquake doublet and seismic crisis in northeastern Taiwan: evidence for dyke intrusion associated with on-land propagation of the Okinawa Trough

SUMMARY Northern Taiwan underwent mountain building in the early stage of the Taiwan orogeny but is currently subjected to post-collisional crustal extension. It may be related to gravitational collapse or to the rifting of the Okinawa Trough, which lies offshore northeastern Taiwan. The Ilan Plain, northeastern Taiwan, which is bounded by the normal fault systems and filled up with thick Pliocene–Pleistocene sedimentary sequences, formed under such an extension environment. Over there on 2005 March 5 two earthquakes with about the same magnitude (M L = 5.9) occurred within 68 s and produced intense aftershocks activity according to the records of Central Weather Bureau Seismic Network of Taiwan. We relocated the earthquake sequence by the three-dimension earthquake location algorithm with the newly published 3D Vp and Vp/Vs velocity model, and determined the first-polarity focal mechanisms of the earthquake doublet. One major cluster of aftershocks which trends E–W and dips steeply to the south can be identified and picked up as a potential fault plane. The focal mechanisms of the two main shocks are both classified as normal type by first-polarity but strike-slip by centroid moment tensor inversion; however two methods both yield consistent E–W strike. Static coseismic deformation was additionally determined from Global Positioning System (GPS) daily solutions at a set of continuous GPS stations and from strong-motion seismographs. These data show NW–SE extension at high angle to the fault plane, which cannot be explained from a simple strike-slip double-couple mechanism. On the other hand, the small vertical displacements and steep fault plane cannot be explained from a simple normal event as well. We present from elastic dislocation modelling that the geodetic data are best explained by significant component of tensile source with centimetre-scale of opening on a 15-km-long fault extending from 1 to 13 km depth. We therefore interpret the crisis as the result of dyke intrusion at the very tip of the Okinawa Trough, which is reasonably driven by backarc spreading.

Coastal uplift mechanisms at Pakarae River mouth: Constraints from a combined Holocene fluvial and marine terrace dataset

One of the major environmental controls on sedimentary systems is tectonics, and thus in order to make quantitative explanations and predictions of the behaviour of sedimentary systems, it is important to quantify tectonic rates and mechanisms. In this study we show how a combined Holocene fluvial and marine terrace dataset can be used to place constraints on coastal uplift mechanisms at Pakarae River mouth, to the east of the Waipaoa sedimentary system. Mapping and surveying of fluvial terraces shows that the terraces can be divided into three sets, (i) PgT, a fill terrace formed during post-glacial sea level rise (~ 10000–7000 cal. yr BP), (ii) a sequence of post-7000 cal. yr BP degradation terraces, and (iii) historical (post ~ AD 1880) flood terraces. A conceptual model of terrace evolution proposes that coseismic uplift has resulted in the observed back-tilting, downstream divergence, and successive abandonment of tectonic terraces. Coastal uplift mechanisms are then examined by comparing the fluvial and marine terrace uplift distribution and the uplift-per-event from the marine terraces with those predicted by forward elastic dislocation models. The models agree with the interpretation that the terrace uplift can be explained by coseismic slip on a steeply west-dipping reverse fault located close to the shore, possibly in combination with rupture of the Hikurangi Margin subduction interface 10–24 km below. This study also provides insights into the tectonic drivers and impacts on the adjacent Waipaoa sedimentary system including: the possible role of subduction earthquakes, growth of structures on the shelf and upper slope, and the role that the interplay between sea level and tectonic controls has on sediment dispersal.

Geodetic exploration of the elastic properties across and within the northern San Andreas Fault zone

Relying on densely spaced GPS data collected between 1996 and 2007 and on InSAR data spanning the 1992–2001 time period, we explore the effects of lateral rheological heterogeneities across the San Andreas Fault near Point Reyes on the interseismic velocity field. We evaluate heterogeneous elastic dislocation models, including an asymmetric model with contrasting rigidities on either side of the San Andreas Fault and models with a narrow compliant fault zone that lead to high near-fault strain rates. We show that we cannot resolve a compliant zone from interseismic surface displacement measurements unless independent constraints on the locking depth exist. We infer an 18 ± 1 mm yr − 1 slip rate on the San Andreas Fault with a 10 ± 2 km locking depth and a 40% higher rigidity to the SW of the fault. At Bodega Bay, GPS and EDM data suggest a compliant zone on the SAF with a 50-to-60% rigidity decrease, but 25 km further south we find no evidence for a weak fault zone. This suggests substantial variability in fault zone properties along the San Andreas Fault.

Triangulation-to-GPS and GPS-to-GPS geodesy in Trinidad, West Indies: Neotectonics, seismic risk, and geologic implications

We estimated horizontal velocities at 25 sites first surveyed in a 1901–1903 British Ordnance Survey triangulation and then resurveyed with GPS in 1994–1995 to identify Trinidad's principal active on-land faults, quantify fault-slip-rates, and test for elastic locking. Our best-fit single-fault elastic dislocation model put 12 ± 3 mm/yr of dextral strike-slip on the Central Range Fault (1–2 km locking depth), an apparently aseismic active fault. The estimated motions also showed statistically insignificant horizontal motion (2.2 ± 1.8 mm/yr of right-slip; 2.7 ± 2.0 mm/yr of N–S shortening) on the eastward on-strike extension of the El Pilar Fault, known to be the active transform fault in Venezuela. Repeat GPS measurements made between 1994 and 2005 at two sites spanning the island north to south showed a 14 ± 3 mm/yr eastward (plate-motion-parallel) dextral velocity differential, consistent with our best-fit historic (1901–1995) fault-slip-rate. Paleoseismology trenching demonstrates that the Central Range Fault cuts <5000-year-old sediment and is capped by ∼550-year-old sediment, suggesting that it may be locked and may have ruptured at least once during this time interval. About ∼5 mm/yr of slip could be taken up on the Los Bajos Fault and additional faults in the offshore south of Trinidad. The existing 1901–1995 and 1994–2005 geodetic data alone cannot resolve whether the Central Range Fault is essentially creeping (≤1–2 km locking depth) or locked to a more standard depth of 10 km.

Impact of megathrust geometry on inversion of coseismic slip from geodetic data: Application to the 1960 Chile earthquake

We analyze the role of megathrust geometry on slip estimation using the 1960 Chile earthquake (MW = 9.5) as an example. A variable slip distribution for this earthquake has been derived by Barrientos and Ward (1990) applying an elastic dislocation model with a planar fault geometry. Their model shows slip patches at 80–110 km depth, isolated from the seismogenic zone, interpreted as aseismic slip. We invert the same geodetic data set using a finite element model (FEM) with precise geometry derived from geophysical data. Isoparametric FEM is implemented to constrain the slip distribution of curve‐shaped elements. Slip resolved by our precise geometry model is limited to the shallow region of the plate interface suggesting that the deep patches of moment were most likely an artifact of the planar geometry. Our study emphasizes the importance of fault geometry on slip estimation of large earthquakes.

Co-seismic and post-seismic pore-fluid pressure changes in the Philippine Sea plate and Nankai decollement in response to a seismogenic strain event off Kii Peninsula, Japan

AbstractNew pressure data from a pair of Ocean Drilling Program (ODP) hydrologic borehole observatories at ODP Sites 1173 and 808, located off Japan in the subducting Philippine Sea plate and in the nearby Nankai accretionary prism, respectively, show clear signals associated with an earthquake swarm off the Kii Peninsula that began on September 5, 2004, roughly 220 km away from the observatory sites. At Site 1173, formation pressures rose by 1.0–1.5 kPa at the time of the largest earthquake (Mw= 7.5), then continued to rise to a total anomaly of 4 kPa during the following 200–300 days. These transients are inferred to reflect co-seismic and slow continuing volumetric contraction of the plate by amounts of roughly 0.2 × 10−6and 0.5 × 10−6, respectively. The sign of the estimated strain is consistent with that predicted with a seismic-moment-constrained elastic half-space dislocation model, but the amplitude is much larger, by roughly a factor of 6 at the time of the main earthquake, and by nearly a factor of 20 when the total pressure-estimated strain at the end of the post-seismic period is compared to that estimated from the total cumulative seismic moment including aftershocks. The simplest inference that can be drawn is that a large component of aseismic slip occurred in the epicentral area. At Site 808, pressure at the deepest monitoring zone just above the subduction decollement fell at the time of the largest earthquakes. This may reflect shear-induced dilatation which would be consistent with strain-or velocity-hardening behaviour along this seaward-most part of the subduction thrust interface.

Shocks in a box: An analogue model of subduction earthquake cycles with application to seismotectonic forearc evolution

We introduce and test an experimental approach to simulate elastoplastic megathrust earthquake cycles using an analogue model and apply it to study the seismotectonic evolution of subduction zones. The quasi‐two‐dimensional analogue model features rate‐ and state‐dependent elastic‐frictional plastic and viscoelastic material properties and is scaled for gravity, inertia, elasticity, friction, and viscosity. The experiments are monitored with a high‐resolution strain analysis tool based on digital image correlation (particle imaging velocimetry, PIV), providing deformation time series comparable to seismologic, geodetic, and geologic observations. In order to separate elastic and nonelastic effects inherent the experimental deformation patterns, we integrate elastic dislocation modeling (EDM) into a hybrid approach: we use the analogue earthquake slip and interseismic locking distribution as EDM dislocation input and forward model the coseismic and interseismic elastic response. The residual, which remains when the EDM prediction is subtracted from the experimental deformation pattern, highlights the accumulation of permanent deformation in the model. The setup generates analogue earthquake sequences with realistic source mechanisms and elastic forearc response and recurrence patterns and reproduces principal earthquake scaling relations. By applying the model to an accretionary‐type plate margin, we demonstrate how strain localization at the rupture peripheries may lead to a seismotectonically segmented forearc, including a tectonically stable shelf and coastal high (&lt;20% plate convergence accommodated by internal shortening) overlying the area of large megathrust earthquake slip. Fifty to 75% of plate convergence is accommodated by internal shortening in the slope region where earthquake slip tapers out toward the trench. The inner forearc region remains undeformed and represents a basin.

Interseismic uplift rates for western Oregon and along‐strike variation in locking on the Cascadia subduction zone

We quantify the spatial pattern of uplift rate in western Oregon and northernmost California using tidal and leveling records to better understand the pattern of interseismic locking on the Cascadia subduction zone. We extend relative sea level time series of the six primary NOAA tide gauges to include all observations from 1925 to 2006. Previously unidentified bench mark instability biases portions of tidal records by ≤1.6 mm a−1 before correction. We determine precise relative uplift rates at the six tidal sites with an adjustment that includes rates of differenced time series as additional constraints. Our analysis of National Geodetic Survey leveling data between tide gauges corrects errors in 1941 leveling, and 184 secondary ties double the number of highest quality uplift rate estimates. Relative uplift rates from leveling are adjusted to the tidal rates, accounting for uncertainties in both data types. Tidal and leveling uplift rates agree within error for all but one of the coastal segments, where we infer systematic leveling error affects the 1988 line. Uplift rates are made absolute using an interval and location‐specific geocentric sea level rise rate of 2.3 ± 0.2 mm a−1. Total propagated one sigma errors for the absolute uplift rates of bench marks are ∼0.4 mm a−1. Along‐strike changes in uplift rate near 45°N and 42.8°N require two distinct changes in locking depth, as inferred from elastic dislocation modeling. The along‐strike changes in locking on this portion of the Cascadia subduction zone interface correlate to the western and southern extent of the mafic Siletzia block in the fore arc.

１９４５年三河地震（Ｍ＝６．８）に伴う地殻変動と震源断層モデルの再検討

This study reexamines the ground deformation and fault slip model of the 1945 Mikawa earthquake (M =6.8), central Japan. We reevaluate two geodetic data sets from the years 1886/1887 and 1955/56 that were obtained from the Geographical Survey Institute; these data sets consist of displacements calculated from the net adjustment of triangulation surveys carried out before and after the Mikawa earthquake. We remove the interseismic deformation and coseismic deformation of the 1944 Tonankai earthquake from the two unique data sets used in our analysis. Maximum coseismic horizontal displacements of over 1.4 m were detected to the west of the Fukozu fault. We estimated the coseismic slip by analyzing our data set. The geometry of the fault planes was adopted from a recent seismicity study and from the surface earthquake fault of this area. The best fit to the data is obtained from two faults along the sections running north and south of the Fukozu and Yokosuka faults. The estimated uniform-slip elastic dislocation model consists of two adjacent planes. The fault also appeared to connect the sections running north and south of the Fukozu and Yokosuka faults. Because it can suitably explain the coseismic deformation due to two earthquake source faults, the earthquake source fault is not admitted under the section for the run. The mechanism is considered to be two reverse faults with right-lateral components. The estimated slips for the two source faults are 2.5 m and 1.4 m, respectively. The pressure axis is directed along NE-SW or E-W. The total seismic moment determined from this model is 1.6 × 1019 Nm, corresponding to Mw=6.7.

Predicting the geodetic signature of MW≥ 8 slow slip events

Elastic dislocation models of geodetic measurements above subduction zones have led to the identification of MW≈ 6.0–7.2 slow slip events (SSEs) that release elastic strain over periods of days to months, but great (MW≥ 8) SSEs have remained unidentified. We extrapolate observations of SSE duration and slip magnitude to show that slip velocity decreases with event magnitude and predict that the slip velocity of MW≥ 8 SSEs is ≤50 mm/yr. The slip velocity for great SSEs may never exceed the plate convergence rate and thus never produce a reversal in trench perpendicular motion. Instead, geodetically constrained estimates of apparent partial elastic coupling on subduction zone interfaces worldwide may be direct observations of ongoing MW≥ 8 silent earthquakes with durations of decades to centuries.

Modeling seismicity rate changes during the 1997 Umbria‐Marche sequence (central Italy) through a rate‐ and state‐dependent model

We model the spatial and temporal pattern of seismicity during a sequence of moderate‐magnitude normal faulting earthquakes, which struck in 1997 the Umbria‐Marche sector of Northern Apennines (Italy), by applying the Dieterich (1994) rate‐ and state‐dependent constitutive approach. The goal is to investigate the rate of earthquake production caused by repeated coseismic stress changes computed through a 3‐D elastic dislocation model in a homogeneous half‐space. The reference seismicity rate is assumed time independent, and it is estimated by smoothing the seismicity that occurred in the previous decade without declustering. We propose an analytical relation for deriving the stressing rate directly from the reference seismicity rate. This allows us to perform a tuning of the constitutive parameter Aσ (where A accounts for the direct effect of friction in the rate‐ and state‐dependent model and σ is the effective normal stress) into the Dieterich model through a maximum likelihood method, which yields for this seismic sequence a best fitting value equal to 0.04 MPa. Our computations show that, although seven out of eight main shocks are located in areas of increased rate of earthquake production, numerous aftershocks are located in seismicity shadows. Our simulations point out that the adopted value of Aσ strongly affects the pattern of both seismicity shadow and areas of enhanced rate of earthquake production. We conclude that solely accounting for static stress changes caused by the main shocks of this seismic sequence is not sufficient to forecast the complex spatial and temporal evolution of seismicity.

Stress interaction between magma accumulation and trapdoor faulting on Sierra Negra volcano, Galápagos

Understanding the state of stress within volcanoes and how it changes with active geophysical processes is important to assess when and where magma may propagate to the surface and initiate an eruption. Observations of volcanic deformation help to constrain parameters of models that can be used to describe these processes and to calculate the resulting stress changes within volcanoes. Here I use geodetic observations to constrain elastic dislocation models of magma accumulation and faulting at Sierra Negra volcano, Galápagos, in the years before the October 2005 eruption, which was the first eruption at Sierra Negra since 1979. Both InSAR and GPS data document a remarkable story of ~ 5 m pre-eruption uplift during 1992–2005, which was accompanied by at least three trapdoor faulting events on an intra-caldera fault system, in January 1998, April 2005, and just before the eruption in October 2005. The pattern of uplift observed in the InSAR data from different time periods during 1992–2005 is consistent with filling and pressurization of a 2.2 km deep sill under the caldera. Modeling results for the trapdoor faulting in April 2005, on the other hand, indicate that slip occurred on a thrust fault that dips steeply (71°) in towards the center of the caldera, and extends from the surface down to the sill at 2.2 km depth. Independently, the calculated stress changes caused by the inflating sill show that the Coulomb Failure Stress change (ΔCFS) at the fault's location is maximized on a 72° dipping thrust fault, agreeing almost exactly with the deformation modeling result, and implying that the inflation triggered the faulting. The calculations also show that the ΔCFS for optimally oriented faults (any strike and dip) is significantly larger in the southern part of the caldera, where the faulting took place, than at any other location. The trapdoor faulting in turn relieved the pressure within the sill, but caused compression to the south of the faults. This suggests that while the faulting provides a mechanism for the sill to thicken and postpone eruptions, it also prevents the sill from growing to the south.

The deformation pattern and fault rate in the Tianshan Mountains inferred from GPS observations

Based on GPS measurements conducted from 1992 to 2006, we present the current crustal movement velocity field for approximately 400 sites in the Tianshan Mountains and their adjacent areas, and estimate slip rates on the major faults using a 2-D elastic dislocation model. Our studies show slip rates within the range of 1–4 mm/a on the NW-SE trending strike-slip faults (such as Talas-Fergana fault) in the Tianshan Mountains. We also found the slip rates on the approximately WE-SN trending gently-dipping detachment fault vary from 10–13 mm/a for the southwest Tianshan Mountains to 2–5 mm/a for the eastern Tianshan Mountains, and to 6–12 mm/a for the Kyrgrz Tianshan. The GPS velocity field reveals that the total convergence is not uniformly distributed across the Tianshan Mountains, with 80%–90% of the N-S shortening absorbed along the southern and northern edges, and relatively little deformation accommodated within the interior. This first-order feature of strain pattern is explained best by underthrusting of adjacent blocks beneath the Tianshan Mountains along a basal detachment fault. We found the occurrence of historical M7–8 earthquakes somewhere in the locked ramp that connects the creeping and locking segments of the detachment, thereby resulting in elastic strain concentration and accumulation around it. The elastic strain confined in the upper crustal layer above the detachment ultimately releases through infrequent great earthquakes in the Tianshan Mountains, resulting in considerable folding and faulting at their margins. The Tianshan Mountains propagated outward and rose progressively as a wedge-shaped block.

Evidence for and implications of a Bering plate based on geodetic measurements from the Aleutians and western Alaska

Global Positioning System (GPS) measurements are used to examine the hypothesis of a clockwise rotating Bering plate. Originally proposed on the basis of seismicity, the Bering plate encompasses the Bering Sea, western Alaska, and the Aleutian Islands. GPS measurements from the Bering plate's interior show south to southwest motions of 3–5 mm/a (where a is years). We construct elastic dislocation models to determine the spatial distribution and intensity of locked patches on the Aleutian subduction interface. We use these to remove interseismic strain from the GPS observation and determine an arc translation velocity for each region of the Aleutians, revealing south and southwest motions of 4–8 mm/a. We combine the arc translation rates with measurements from the Bering plate's interior sites and estimate the Euler pole for the Bering plate relative to North America to be located at 42.5°N, 121.3°E with an angular speed of 6.0°/Ma. The clockwise rotation of the Bering plate may cause left lateral faulting in interior Alaska. The Bering plate's interaction with south‐central Alaska may be responsible for the decreased slip rate on the western Denali fault and for contraction across the central Alaska Range. We analyze slip partitioning along the Aleutian arc on the basis of both GPS measurements and slip azimuths of thrust earthquakes and find a systematic discrepancy between plate convergence direction and slip azimuths. We conclude that slip partitioning in the back arc only develops west of Amchitka Pass, whereas slip partitioning in the fore arc is present throughout the arc.

Fracture permeability created by perturbed stress fields around active faults in a fractured basement reservoir

Several researchers have suggested that perturbed stress fields associated with active faults significantly affect flow properties in the subsurface. To examine this insight quantitatively, we combine an elastic dislocation model of active faults and a stress-compliant function for fracture apertures to evaluate flow properties in a fractured basement reservoir in the Yufutsu field, Japan. The most productive well in the reservoir shows about 90 of rotation of the axes of horizontal stresses along the well trajectory, whereas the directions of horizontal stresses at nonproductive wells are commonly oriented consistently with those of the regional stresses. Additionally, results of step-rate hydraulic injection tests at the nonproductive well indicate that fracture apertures fluctuate significantly in response to the magnitude of stresses normal to the fracture surfaces. These observations support the important effect of perturbed stress fields on flow properties. The observed stress orientation profiles are correlated to those from a geomechanical model. Nonproductive wells were drilled in the area where the regional stress state prevails, and the most productive well penetrates the area near the tips of active faults, where the stress concentration leads to enhancements in fracture permeability by opening or shearing. The modeled perturbed stress fields combined with a stress-compliant function for opening of fracture apertures can explain the observed difference of well performances to the first order. The model demonstrates that areas near the tips of active faults have high potentials for hydrocarbon production in fractured basement reservoirs.

Experimental examination of displacement and strain fields in an edge dislocation core

We present a displacement and strain analysis of edge dislocation core in gold. The displacement and strain field around the edge dislocation were mapped by geometric phase analysis of high-resolution transmission electron microscopy images. The displacement and strain measurement results were compared with the isotropic elastic theory dislocation model, the anisotropic elastic theory dislocation model, the Peierls–Nabarro dislocation model and the Foreman dislocation model ( a = 4). These comparisons show that the Peierls–Nabarro model is the most appropriate theoretical model to describe the deformation fields of the dislocation core.

Modelling of the 1986 Kalamata (SW Greece) earthquake faulting using geodetic data

Elastic dislocation modelling of high accuracy repeated levelling data, constrained by seismological and structural data, permits a refinement of the seismic fault model of the 1986, Kalamata (SW Greece mainland), M S = 5.8 destructive earthquake. The authors' preferred solution is a blind normal fault, selected on the basis of minimum misfits between observed and predicted elevation changes. This fault pattern is broadly consistent with seismological and geologic evidence.