Release Of Elastic Strain Research Articles

Physical mechanism for nanocrystalline NiTi alloy with ultrasmall-sized grains exhibiting one-way shape memory effect without temperature-induced phase transformation

In the present work, a novel finding is that nanocrystalline NiTi alloy with ultrasmall-sized grains (where the diameter of grains is less than or equal to 10 nm) presents one-way shape memory effect (OWSME) without temperature-induced phase transformation, where the involved physical mechanism is revealed by combining experiments with molecular dynamics simulation (MD). The results show that fraction of grain boundaries (GBs) is so much that temperature-induced martensitic transformation is suppressed, but it leads to a certain unrecoverable strain. The following loading results in increase of strain and decrease of Gibbs free energy, which leads to stress-induced martensitic transition. After unloading, Gibbs free energy is increased by the release of elastic strain, which leads to partial reverse martensitic transition. Consequently, OWSME in nanocrystalline NiTi alloy with ultrasmall-sized grains is aroused by retained stress-induced martensitic transition followed by its reverse phase transition rather than temperature-induced one followed by its reverse phase transition.

Normal Faulting Movement During the 2020 Mw 6.4 Yutian Earthquake: A Shallow Rupture in NW Tibet Revealed by Geodetic Measurements

The ENE striking Longmu Co fault and the North Altyn Tagh left-lateral slip fault have led to the complex regional structure in the northwestern Tibetan Plateau, resulting in a series of normal faulting and strike slip faulting earthquakes. Using both the ascending and descending Sentinel-1A/B radar images, we depict the coseismic deformation caused by the 2020 Yutian Mw 6.4 earthquake with a peak subsidence of ~ 20 cm. We determine the seismogenic fault geometry by applying the Bayesian approach with a Markov Chain Monte Carlo sampling method, which can better characterize the posterior probability density functions of the source model parameters. The estimation results reveal that the earthquake is a normal faulting event with a moderate strike slip component. Based on the optimal fault geometry model, we extend the fault plane and invert for the distributed coseismic slip model. The optimal slip model shows that the coseismic slip is mainly concentrated at shallow depths of 3–10 km with a maximum slip of ~ 1.0 m. Our preferred geodetic coseismic model exhibits no surface rupture, which may likely be due to the shallow slip deficit in the uppermost crust. We calculate the combined loading effect of the Coulomb failure stress changes induced by the coseismic dislocations and postseismic viscoelastic relaxation of the 2008 Mw 7.1, 2012 Mw 6.4 and 2014 Mw 6.9 Yutian events. Our study demonstrates that the three preceding major Yutian shocks were insufficient to trigger the 2020 Yutian earthquake, which we consider perhaps reflects the natural release of elastic strain accumulated mainly through localized tectonic movement. We attribute the 2020 Yutian event to the release of extensional stress in a stepover zone controlled by the Longmu Co and the North Altyn Tagh sinistral strike slip fault systems. The seismic risk in the southwest end of the North Altyn Tagh fault has been elevated by the Yutian earthquake sequences, which require future attention.

Seismic Moment Release Data in Earthquake Catalogue: Application of Hurst Statistics in Delineating Temporal Clustering and Seismic Vulnerability

ABSTRACT Sequential cumulative moment release data of macro-earthquakes (Mw≥4.3) of seventeen seismic zones (A to Q) belonging to NE-Himalaya, Burmese-Andaman arc and West-Sunda arc are analysed by Hurst analysis, a non-parametric statistical procedure to identify clustering of low and high values in a time series. The moment release in a zone occurs in alternate positive, negative and positive sloping segments forming a wave like pattern with intervening small horizontal segment. The negative sloping segments indicate decelerated moment release pattern or temporal slackening of elastic strain release with high b–value (>0.95). The horizontal segment indicates temporal clustering of moderate magnitude events/seismic moments with moderate b-values (0.8–0.95). The positive segment is characterised by accelerated moment release within a short span of time indicating temporal clustering of larger magnitude earthquakes/seismic moments and exhibit lowest b–value (<0.7). All zones attest moderate to high Hurst K values, range 0.7-0.86. The pattern in Hurst plots, specially a reversal of trend after prolong negative slope is used for earthquake prognostication in the seismic zones. Our analysis shows that most of the zones register a notable reversal of Hurst clustering trend after a prolonged negative slope which is accompanied by a major earthquake near its end. However, South Burma region (Zone-I) and Tripura fold belt and Bangladesh Plain (Zone-K) do not show any moderate or large shock around the end of the negative sloping trend in Hurst plot. Hence, these two zones can be considered more prone to produce moderate to larger earthquakes in future.

Use of Plastic Correction Formula to Improve Accuracy of Welding Residual Stress Test with Blind-Hole Method

The blind-hole method is the most widely used approach to experimentally determine the distribution of residual stress. This paper aims to improve test accuracy of welding residual stress and conducts an experimental study on the strain release factors involved when using the blind-hole method for Q235 and Q345, two steels commonly used in building structures. The ranges of strain release factors A and B in the elastic stage, the effects of strain release factors on residual stress calculated values, and the plastic corrected strain release factors are analyzed considering of the effect of plastic deformation around the blind hole on measurement accuracy. Finally, a simplified calculation formula to determine strain release factors is proposed for use with the blind-hole method. Results show that in the elastic stage, strain release factor A for Q235 and Q345 ranges from −0.399 to −0.525 and strain release factor B from −0.791 to −0.960. Changing the strain release factors A and B shows that calculated residual tensile stress varies in relation to a decrease in both factor values. However, there is a increase in calculated residual compressive stress with a decrease in the strain release factor A value, but there is an decrease with a decrease in strain release factor B value. Calculated residual stress applied to elastic strain release factors is compared with that applied to amended plastic strain release factors for Q235 steel. The maximum deviation between calculated residual stress and test stress is reduced from 21.1 to 1.0%, and for Q345 steel from 26.5 to 1.2%. It is thus evident that the plastic correction formula proposed in this paper can be used in calculations when conducting a residual stress test.

Strain release at the trench during shallow slow slip: The example of Nicoya Peninsula, Costa Rica

AbstractThe near‐trench behavior of subduction megathrust faults is critical for understanding earthquake hazard and tsunami generation. The shallow subduction interface is typically located in unconsolidated sediments that are considered too weak to accumulate elastic strain. However, the spectrum of shallow fault slip behavior is still elusive, due in large part to the lack of near‐field observations. Here we combine measurements from seafloor pressure sensors near the trench and an onshore GPS network in a time‐dependent inversion to image the initiation and migration of a well‐documented slow slip event (SSE) in 2007 at the Nicoya Peninsula, Costa Rica. Our results show that the shallow SSE initiated on the shallow subduction interface at a depth of ~15 km, where pore fluid pressure is inferred to be high, and propagated all the way to the trench. The migrating event may have triggered a second subevent that occurred 1 month later. Our results document the release of elastic strain at the shallow part of the subduction megathrust and suggest prior accumulation of elastic strain. In conjunction with near‐trench shallow slow slip recently reported for the Hikurangi subduction zone and trench breaching ruptures revealed in some large earthquakes, our results suggest that near‐trench strain accumulation and release at the shallower portions of the subduction interface is more common than previously thought.

Accumulation of permanent deformation during earthquake cycles on reverse faults

AbstractA two‐dimensional viscoelastic finite element model with a discrete stick‐slip thrust fault is used to investigate tectonic strain accumulation and release associated with repetitive earthquakes. Results show that although interseismic and coseismic motions are opposite in sign, they generally do not completely cancel each other over a seismic cycle, as normally presumed in elastic rebound theory. Complete elastic strain release adjacent to dip‐slip faults is inhibited by gravity, so that permanent deformation accumulates in the lithosphere with time. In the models, this permanent deformation is observed at the surface as large‐scale upwarping of a hanging wall anticline and depression of an adjacent footwall foreland basin. The results are supported by observation of similar features adjacent to reverse faults in active collisional mountain belts and along the coastal margin of some modern subduction zones.

Revisiting the last major eruptions at Stromboli volcano: inferences on the role of volatiles during magma storage and decompression

Abstract Stromboli is a unique open conduit volcano and a natural laboratory for investigating how volatiles migrate and concentrate under dynamic conditions. Fluid phases are involved in magma decompression and pressurization, modulate Strombolian activity and govern magma rise and fragmentation processes. Here, we have revisited the available data on the last two major eruptions at Stromboli volcano and concentrated our analysis on the 2007 eruption. First, we analysed petrological-geochemical data to assess equilibrium conditions by using standard thermobarometry; we then used a grid of selected reactions which involve solid-melt-fluid equilibria to better constrain the P – T regimes that adequately describe our system. Primitive hydrous basaltic melts, reported in literature and preserved as melt inclusions in olivine (with 2.3–3.8 wt% of H 2 O and 890–1590 ppm CO 2 ), are in equilibrium with forsteritic olivine and a diopsidic clinopyroxene at average pressures of 260 (±47) MPa for temperatures approaching 1170 (±17) °C and calculated (mole fraction of CO 2 within the melt) in the range 0.60–0.76. Ca-rich or ultracalcic melts are regarded as the result of decompression along a steep adiabatic and/or isothermal curve. During this process the magma will cross-cut the stability field of diopside and enter the liquidus field. The earlier crystallized diopside is destabilized and reacts with the coexisting liquid phase leading to the formation of ultracalcic melts. Ejected golden pumices (with 2–3 wt% H 2 O) are in equilibrium with Ca-pyroxene, forsteritic olivine and anorthitic plagioclase at 150–220 MPa and temperatures of 1120–1150 °C. Evolved melt inclusions (substantially degassed) in less magnesian olivine ( c. Fo 70 ) of the scorias show average equilibration pressures of 78 (±20) MPa and temperatures of 1138 (±14) °C. In summary, the higher P–T regimes associated with the origin of primitive melt inclusions are representative of the base of the chamber, where the ferromagnesian phases may crystallize and cumulate. The magma with a bulk composition typical of the pumices is stored in the middle and main part of the chamber (likely its axial sector) and these materials are erupted during paroxysmal and, more rarely, major explosions. Finally, more evolved melt inclusions found in the olivine of the scorias are indicative of crystallization within the conduit or its root zone connected to the upper part of the chamber. Pure extensional regimes and recent geophysical data suggest the existence of a prolate ellipsoidal magma chamber below Stromboli. To constrain its volume we estimated the magma volumes associated with SO 2 degassing (during the 2007 major eruption) by applying a refined petrological model that allowed us to estimate the magma fluxes in the subvolcanic region (i.e. the magma flux entering the degassing zone). The long-term trend of this magma flux follows an overall exponential decay, typical of pressurized magmatic systems, and indicates that magma rise was accompanied and followed by slow decompression. This trend was shown to be consistent with release of elastic strain accumulated either by pressurization of the rocks surrounding the magma reservoir, by pressurization of the magma itself or both. By analysing the reservoir elastic response during magma decompression, we found that the current Stromboli magma chamber volume may be adequately constrained to 1–2 km 3 .

Hanging wall deformation of a seismogenic megasplay fault in an accretionary prism: The Nobeoka Thrust in southwestern Japan

The structure and occurrence of deformation within the hanging wall of the Nobeoka Thrust in Kyushu, Japan, was investigated to understand the dynamic aspects of splay faulting in relation to seismic events. From field observations, hanging wall is suggested to have undergone four phases of deformation. The first phase involved horizontal shortening, as documented by folding and thrusting, followed by a phase of vertical loading shown by the development of horizontal slaty cleavages, pressure solution, and cleavage-parallel mineral vein precipitation. A third phase involved shearing, and deformation along cleavage restricted to near the Nobeoka Thrust, while the fourth phase produced widespread, brittle fracturing associated with the development of pseudotachylyte-bearing faults and tension crack filling veins high angle to cleavage. These four phases can be explained as follows.During the inter-seismic period, an extensionally stable taper was maintained in the inner wedge of the accretionary prism by dominant vertical loading (σ1), in combination with a lesser amount of horizontal compression (σ2) related to the locking of the mega-thrust. Elastic strain energy in the hanging wall of the inner wedge was co-seismically released by slip on the mega-thrust and horizontal shortening in the outer wedge associated with dynamic ductile weakening of the fault plane. This sudden release of elastic strain caused brittle fracturing with σ1 at a high angle to the shear surface of the Nobeoka Thrust, most of the displacement resulting from deformation of the footwall.

Rupture process of the 2011 Tohoku-oki earthquake and absolute elastic strain release

[1] On 11 March 2011, the Tohoku-oki earthquake in eastern Japan and the devastating tsunami that followed it caused severe damage and numerous deaths. To clarify the rupture process of the earthquake, we inverted teleseismic P-wave data applying a novel formulation that takes into account the uncertainty of Green's function, which has been a major error source in waveform inversion. The estimated seismic moment is 5.7 × 1022 Nm (Mw = 9.1), associated with a fault rupture 440 km long and 180 km wide along the plate interface. The source process is characterized by asymmetric bilateral rupture propagation, but we also found continuous slips up-dip from the hypocenter, which led to a large maximum slip (50 m), long slip duration (90 s), and a large stress drop (20 MPa). The long slip duration, large stress drop, extensional (normal faulting) aftershocks in a previously compressional stress regime, and low-angle normal slips at approximately the depth of the plate interface suggest that the earthquake released roughly all of the accumulated elastic strain on the plate interface owing to exceptional weakening of the fault. The stress accumulated on the plate interface was about 20 MPa near the trench and 0–10 MPa in the down-dip source region.

Some characteristics of the seismicity of the Tyrrhenian Sea Region

In the first p a r t of the paper the seismic strain release of the T y r r h e n i a n Sea Region (including Italy), as the function of time, is examined on the basis of t h e d a t a of the e a r t h q u a k e s t h a t took place f r om 1901.01.01 to 1970.12.31, between the northern l a t i t u d e s of 34° and 44° and between the eastern longitudes of 8° and 18.5°, respectively. All registered shocks with a R i c h t e r - m a g n i t u d e of 5.5 or over it were considered, i n d e p e n d e n t l y f r om t h e focal d e p t h . Three periods were recognized in the a c t i v i t y ; t h e lengths of which are not t h e same, however. I n the second p a r t the elastic strain release in accordance with the focal d e p t h of t h e same e a r t h q u a k e s is t r e a t e d briefly. It was found t h at t h e t o t a l strain-release had a maximum value in t h e depth between 0 and 74 kms and there was a minimum between the depth of 300 and 524 kins with an interval between 375 and 449 kms within which no earthquakes occurred at all. The general p a t t e r n of the d i s t r i b u t i o n of seismicity as t h e f u n c t i o n of hypocentral d e p t h reminds to the well-known picture, one can experience in other regions where i n t e r m e d i a t e and deep shocks occur. This s t a t e m e n t is consistent w i t h t h e idea, according to which t h e seismicity of t h e Tyrrhenian Sea Region can be discussed and explained in t h e light of t h e theory of new global tectonics. F i n a l l y , in the t h i r d p a r t of the study, the authors have s t a t e d t h at in some cases multiple events occurred b e n e a t h t h e Tyrrhenian Sea Region. Such multiple seismic events were detected in the case of other areas, such as the Fiji-Tonga-Kermadec Region, the seismic belt of South America etc., — but, according to the knowledge of t h e authors, this is t h e first occasion when multiple seismic events are demonstrated in the Tyrrhenian Sea Region.

Two-way shape memory effect in polymer laminates

Novel polymer laminate exhibiting two-way shape memory effect has been prepared by layer technique with the shape memory polymer and elastic polymer. In this paper, we demonstrate the two-way shape memory behavior, i.e., bending on heating and reverse bending on cooling; describe the preparation procedure; and investigate its two-way shape memory mechanism. Finally, it suggests that the mechanism can be ascribed to the release of elastic strain of shape memory polymer layer upon heating, and the elastic strain recovery induced by the bending force of substrate layer upon cooling.

Chloride vapor-phase epitaxy of gallium nitride on silicon: Effect of a silicon carbide interlayer

A new approach is described, according to which the use of a thin silicon carbide (SiC) interlayer ensures the suppression of cracking and the simultaneous release of elastic strain in gallium nitride (GaN) epilayers grown by hydride-chloride vapor-phase epitaxy (HVPE) on 1.5-inch Si(111) substrates. Using this method, 20-μm-thick GaN epilayers have been grown by HVPE on Si substrates with AlN (300 nm) and SiC (100 nm) interlayers. A high quality of the obtained GaN epilayers is confirmed by the photoluminescence spectra, where an exciton band with hvmax = 3.45 eV and a half-width (FWHM) of 68 meV is observed at 77 K, as well as by the X-ray rocking curves exhibiting GaN(0002) reflections with a half-width of ωϑ = 600 arc sec.

Seismicity Associated with the Sumatra–Andaman Islands Earthquake of 26 December 2004

AbstractThe U.S. Geological Survey/National Earthquake Information Center (usgs/neic) had computed origins for 5000 earthquakes in the Sumatra–Andaman Islands region in the first 36 weeks after the Sumatra–Andaman Islands mainshock of 26 December 2004. The cataloging of earthquakes of mb (usgs) 5.1 and larger is essentially complete for the time period except for the first half-day following the 26 December mainshock, a period of about two hours following the Nias earthquake of 28 March 2005, and occasionally during the Andaman Sea swarm of 26–30 January 2005. Moderate and larger (mb ≥5.5) aftershocks are absent from most of the deep interplate thrust faults of the segments of the Sumatra–Andaman Islands subduction zone on which the 26 December mainshock occurred, which probably reflects nearly complete release of elastic strain on the seismogenic interplate-thrust during the mainshock. An exceptional thrust-fault source offshore of Banda Aceh may represent a segment of the interplate thrust that was bypassed during the mainshock. The 26 December mainshock triggered a high level of aftershock activity near the axis of the Sunda trench and the leading edge of the overthrust Burma plate. Much near-trench activity is intraplate activity within the subducting plate, but some shallow-focus, near-trench, reverse-fault earthquakes may represent an unusual seismogenic release of interplate compressional stress near the tip of the overriding plate. The interplate-thrust Nias earthquake of 28 March 2005, in contrast to the 26 December aftershock sequence, was followed by many interplate-thrust aftershocks along the length of its inferred rupture zone.

Late Pleistocene to Holocene record of changing uplift rates in southern Calabria and northeastern Sicily (southern Italy, Central Mediterranean Sea)

A combination of published and new radiometric dates on uplifted Holocene fossil beaches from northeastern Sicily and southern Calabria (southern Italy) is compared with the altitude of the inner margin of the Last Interglacial (LIg) (Late Pleistocene, ∼124 ka) and older marine terraces in order to gain a regional-scale outline of uplift rates and their temporal changes in a region which is one of the fastest uplifting sectors of the Central Mediterranean Sea. Late Holocene radiocarbon dates from Ioppolo (southern Calabria) and Ganzirri (northeast Sicily), two newly discovered sites are here presented for the first time. The Holocene uplift rates are highest at St. Alessio and Taormina in eastern Sicily (2.4 mm/y) and at Scilla in southwestern Calabria (2.1 mm/y), two sites located across the Messina Straits and which separate the island of Sicily from mainland Italy. Uplift rates decrease towards the south and north from this centre of uplift. Late Holocene uplift rates show an apparent increase of between 64 and 124% when compared with the longer-term uplift rates calculated from the LIg highstand terraces. Furthermore, we discovered that the locations of fastest Late Pleistocene and Late Holocene uplift rates spatially coincide. To what extent the Holocene increase in uplift rates results from incomplete elastic strain release along the major extensional faults which frame the seismotectonic of the area, or indicate a true change in regional tectonic processes, is not resolved. Nonetheless, the heterogeneity of uplift, with a well-defined centre that crosses the Messina Straits, and its persistence at different time-scales indicates a tight connection between wider regional processes and fault-related displacement in controlling crustal instability in this area.

Strain localisation within ductile shear zones beneath active faults: The Alpine Fault contrasted with the adjacent Otago fault system, New Zealand

The Alpine Fault accommodates around 60–70% of the 37 mm/yr oblique motion between the Australian and Pacific plates in the South Island of New Zealand. Uplift on the fault over the past 5 Ma has led to the exhumation of the deep-seated mylonite zone alongside the present surface trace. Shear strain estimates in the mylonites reach 200–300 in the most highly strained rocks, and provide an integrated displacement across the zone of 60–120 km. This is consistent with the amount of displacement during the last 5 Ma, suggesting that displacement on the fault is localised within a 1–2 km wide ductile shear zone to depths of 25–30 km. Existing geodetic data, together with Late Quaternary slip rate and paleoseismic data, are consistent with the steady build-up and release of elastic strain in the upper crust driven by ductile creep within a narrow mylonite zone at depth. Faults of the Otago Fault System form a parallel array east of the Alpine Fault and accommodate c. 2 mm/yr contraction. Long periods of quiescence on individual structures suggest episodic, or “intermittently characteristic”, behaviour. This is more consistent with failure on faults within an elastico-frictional upper crust above a ductile lower crust. Localisation of crustal deformation may be initiated by inherited weaknesses in the upper crust, with downward propagation of slip causing strain weakening within the ductile zone immediately beneath. Inherited structures of great length focus a greater amount of displacement and hence more rapidly develop underlying zones of ductile shear.

Microstructure and magnetic properties of sputtered Fe–Pt thin films

The characterization of rf magnetron-sputtered Fe–Ptthin films at various compositions (Pt = 15,24, 46 and 78 at%) is reported. X-ray diffraction studies onannealed Fe–46%Pt thin films at 600 °Crevealed an ordered L10 γ2-FePtphase with fct structure whereas annealed Fe–24%Pt and Fe–78%Ptfilms exhibited ordered γ1-Fe3 Ptand γ3-FePt3phases, respectively. The effects of argon quenching and rapid thermalannealing (RTA) on the structural and magnetic properties areinvestigated. When the films are annealed at 600 °C for 1 h andthen quenched to room temperature in argon gas, ordered γ2-FePt with L10phase is obtained. Argon-quenched and rapid thermal annealed films exhibitmicrotwins in scanning electron microscopy analysis. The appearance ofmicrotwins may be attributed to the planar defects developed in the FePt filmsdue to the release of elastic strain during annealing. The saturation magnetizationis found to increase with ferrous content in the films. Argon-quenchedFe–46%Pt films exhibited larger saturation magnetization than RTA-processedfilms. The large value of saturation magnetization obtained from M– H hysteresisindicates the predominant existence of the hard fct γ2-FePt phase. Thecombined effects of twins, long-range order and the hard γ2-FePtphase on the magnetic properties are discussed.

Volumetric characteristics of lava flows from interferometric radar and multispectral satellite data: the 1995 Fernandina and 1998 Cerro Azul eruptions in the western Gal�pagos

We have used a suite of remotely sensed data, numerical lava flow modeling, and field observations to determine quantitative characteristics of the 1995 Fernandina and 1998 Cerro Azul eruptions in the western Galapagos Islands. Flank lava flow areas, volumes, instantaneous effusion rates, and average effusion rates were all determined for these two eruptions, for which only limited syn-eruptive field observations are available. Using data from SPOT, TOPSAR, ERS-1, and ERS-2, we determined that the 1995 Fernandina flow covers a subaerial area of 6.5×106 m2 and has a subaerial dense rock equivalent (DRE) volume of 42×106 m3. Field observations, ATSR satellite data, and the FLOWGO numerical model allow us to determine that the effusion rate declined exponentially from a high of ~60–200 m3 s-1 during the first few hours to <5 m3 s-1 prior to ceasing after 73 days, with a mean effusion rate of 4–16 m3 s-1. Integrating the ATSR-derived, exponentially declining effusion rate over the eruption duration produces a total (subaerial + submarine) DRE volume of between 27 and 100×106 m3, the range in values being due to differing assumptions about heat loss characteristics; only values in the higher part of this range are consistent with the independently derived subaerial volume. Using SPOT, TOPSAR, ERS-1, and ERS-2 data, we determine that the 1998 Cerro Azul flow is 16 km long, covers 16 km2, and has a DRE volume of 54×106 m3. FLOWGO produces at-vent velocity and effusion rate values of 11 m s-1 and ~600 m3 s-1, respectively. The velocity value agrees well with the 12 m s-1 estimated in the field. The mean effusion rate (total DRE volume/duration) was 7–47 m3 s-1. Dike dimensions, fissure lengths, and pressure gradients along the conduit based on magma chamber depth estimates of 3–5 km produce mean effusion rates for the two eruptions that range over nearly four orders of magnitude, the range being due to uncertainty in the magma viscosity, dike dimensions, and pressure gradient between magma chamber and vent. Although somewhat consistent with mean effusion rates from other techniques, their wide range makes them less useful. The exponentially declining effusion rates during both eruptions are consistent with release of elastic strain being the driving mechanism of the eruptions. Our results provide independent input parameters for previously published theoretical relationships between magma chamber pressurization and eruption rates that constrain chamber volumes and increases in volume prior to eruption, as well as time constants of exponential decay during the eruption. The results and theoretical relationships combine to indicate that at both volcanoes probably 25–30% of the volumetric increase in the magma chamber erupted as lava onto the surface. In both eruptions the lava flow volumes are less than 1% of the magma chamber volume.

Elastic rebound following the Kocaeli earthquake, Turkey, recorded using synthetic aperture radar interferometry

A basic model incorporating satellite synthetic aperture radar (SAR) interferometry of the fault rupture zone that formed during the Kocaeli earthquake of August 17, 1999, documents the elastic rebound that resulted from the concomitant elastic strain release along the North Anatolian fault. For pure strike-slip faults, the elastic rebound function derived from SAR interferometry is directly invertible from the distribution of elastic strain on the fault at criticality, just before the critical shear stress was exceeded and the fault ruptured. The Kocaeli earthquake, which was accompanied by as much as ∼5 m of surface displacement, distributed strain ∼110 km around the fault prior to faulting, although most of it was concentrated in a narrower and asymmetric 10-km-wide zone on either side of the fault. The use of SAR interferometry to document the distribution of elastic strain at the critical condition for faulting is clearly a valuable tool, both for scientific investigation and for the effective management of earthquake hazard.

Surface segregation in Ni(W) solid solution

The surface composition of Ni–7%W solid solution equilibrated under UHV in the range 750–1100 K was determined by means of quantitative Auger electron spectroscopy. Only part of the excess tungsten accumulated at the sputter-cleaned surface dissolved upon subsequent annealing, and from the temperature dependence of the residual W equilibrium concentration, quantified for two different in-depth distribution models, segregation enthalpies and excess entropies are derived. The observed tungsten surface segregation tendency indicates dominance of elastic strain release over weakened interatomic bonding driving forces in this solid solution. Tungsten segregation levels are relatively low because of the small net energetic driving force, and due to a suppressing excess entropy effect. Adsorption of oxygen on the alloy surfaces enhances W segregation at elevated temperatures due to preferential WO interactions.

Face-related segregation reversal at Pt50Ni50 surfaces studied with the embedded atom method

The segregation to the three low-index surfaces of a Pt50Ni50 single crystal is modelled by Monte Carlo simulations combined with the embedded atom method (EAM). Using the best fit EAM parameters from the literature for the six transition metals of the Ni and Cu groups does not yield satisfactory results. In this work the EAM parameters are recalculated and optimised exclusively for the Pt–Ni alloy system under study. Only then does EAM reliably reproduce the driving forces for segregation.The experimental results [Y. Gauthier et al., Phys. Rev. B 31 (1985) 6216; Y. Gauthier et al., Phys. Rev. B 35 (1987) 7867; S.M. Foiles, in: P.A. Dobson, A. Miller (Eds.), Surface Segregation Phenomena, CRC Press, Boca Raton, FL, 1990, p. 79] reveal a face-related segregation reversal for the Pt50Ni50 single crystal. It appears from the simulations that this is caused by a relatively small difference in surface energy in close competition with the elastic strain release. At the open (110) surface the difference in surface energy dominates causing Ni segregation. At the (100) and (111) surfaces the difference in surface energy is overpowered by the elastic strain leading to Pt segregation. The simulations are in good agreement with the experimental results and reproduce quantitatively the Ni segregation to the (110) surface and the Pt segregation to the (100) and (111) surfaces. Only at the (110) surface significant relaxations are predicted in good agreement with experimental evidence.Atomic vibrations can be included by allowing a large number of very small displacements or with a more classical treatment of vibrational entropy. Both approaches yield the same results and show that the inclusion of atomic vibrations is important only for the (110) surface and tend to attenuate the Ni segregation profile.