Magnetic flux leakage (MFL) is the most widely used non-destructive evaluation (NDE) technique for operating gas and oil transmission pipelines. The Queen’s Applied Magnetics Group (AMG) has been studying MFL signals from dents for the past 5 years, and recently began considering MFL signals from gouges, and gouge/dent combinations. It is believed that MFL signals from gouges may arise from three factors: the gouge geometry, residual stresses, and a severe plastically deformed layer that is often present at the base of the gouge. The last factor has been studied by another MSc student, Kris Marble. The present thesis work primarily considers the effects of the first two factors – gouge geometry in combination with residual stress. Samples containing realistic gouges, produced under field-like conditions, were obtained from two sources - Stress Engineering Services (SES) in Houston, Texas and GdF Suez in St. Denis, France. At SES, ten different gouges on five pipes (two on each pipe) with increasing severity were produced for the current thesis project. Three gouged pipe samples were obtained from GdF Suez. The bulk of the thesis study involved experimental MFL measurements made for each of the gouges and gouge/dents of SES samples in the study, on both the outer and inner surface, and in some cases when the pipe wall was under pressure. The experimentally obtained MFL signals were interpreted by comparison with the expected MFL geometry-only signals (obtained using magnetic modeling) along with the knowledge of the residual stress information obtained from the neutron diffraction measurements. Various results were obtained and concluded. The neutron diffraction was also done on three GdF Suez samples. The results from one sample were used to model the residual stress distribution around the sample and the modeled MFL signals were compared with the experimental MFL signals. The modeled signals are able to account for most features in the experimental results. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-01-29 14:13:54.535

Lors d'un tremblement de terre, les transformations physiques et chimiques qui surviennent le long d'une zone de glissement vont conduire à l'altération et à la formation de minéraux. La gouge contient des minéraux magnétiques, qui peuvent être formés sous l'action combinée de la chaleur frictionnelle et par l'action chimique en relation avec les fluides. Ainsi, la gouge a la capacité de se comporter comme un enregistreur magnétique pendant un tremblement de terre. Il s'agit là d'une nouvelle méthode pour identifier les zones de tremblements de terre de glissement. En outre,les minéraux magnétiques initiaux, altérés, et néoformés peuvent être utilisés comme traceurs de certains processus physico chimique.Dans cette étude, nous étudions le magnétisme des roches et l'enregistrement paléomagnétique de la gouge de faille active de Chelungpu qui héberge, entre autres,la zone de glissement principale du tremblement de terre de Chi-Chi (Mw 7.6, 1999,Taiwan). Nous avons bénéficié pour cette étude d'échantillons non altérés provenant des carottes du forage B Taiwan Chelungpu-fault Drilling Project (TCDP). Nous avons également échantillonné la faille de Chelungpu à l'affleurement pour une caractérisation des nanoparticules. Cette caractérisation vise à estimer l'énergie de fracture dans la gouge de faille. / During an earthquake, the physical and the chemical transformations along a slip zone lead to alteration and formation of minerals within the gouge layer of a mature fault zone. The gouge contains magnetic minerals, which could be formed under the combined action of friction heat and fluid. Thus, gouge has the capacity to behave as a magnetic recorder during an earthquake. This constitutes a conceivable way to identify earthquakes slip zones. Besides, altered and neoformed magnetic minerals can be used as tracers of some earthquake processes. In this study, we investigate the rock magnetism and paleomagnetism of the Chelungpu fault gouge that hosts the principal slip zone of the Chi-Chi earthquake (Mw 7.6, 1999, Taiwan) using Taiwan Chelungpu-fault Drilling Project (TCDP) hole-B core samples. We also took a Chelungpu fault outcrop sample for identification of nanoparticle, which associated with fracture energy estimation in fault gouge.

Cette thèse vise à étudier les propriétés thermo-poro-mécaniques de roches de faille, à partir de l'analyse structurale et microstructurale d'une faille aujourd'hui à l'affleurement et à partir d'expériences menées en laboratoire, en vue de déterminer les processus qui contrôlent l'efficacité de deux mécanismes responsables de d'affaiblissement cosismiques : la pressurisation thermique et le mécanisme d'affaiblissement par drainage. L'étude de terrain a été conduite sur deux affleurements appartenant à une faille décrochante potentiellement active appartenant au système de failles du Chugoku occidental (Japon) : la faille d'Usukidani. Le travail expérimental a quant à lui été mené dans le laboratoire de déformation des roches de l'Université de Kyoto. Les résultats majeurs de ce travail sont exposés ci-dessous. <br /> Les propriétés hydrologiques et poro-élastiques de la gouge et de la brèche de la faille d'Usukidani ont été determinées à partir d'échantillons prélevés sur le terrain. Ces données hydrauliques ont ensuite été utilisées dans un modèle numérique afin d'évaluer l'importance du phénomène de pressurisation thermique dans le cas d'un glissement cosismique le long de la zone de glissement principale et le long de zones de glissement secondaires. Les résultats de cette modélisation suggèrent que le mécanisme de pressurisation thermique n'est efficace que si la rupture reste localisée le long des zones de glissement contenant de la gouge, avec comme facteur de contrôle l'épaisseur de cette zone de glissement. <br /> Afin d'identifier les processus dynamiques particulaires responsables de l'affaiblissement cosismique dans la zone de glissement, plusieurs essais de friction ont été menés sur une machine à cisaillement annulaire. Ces expériences ont été conduites à des vitesses cosismiques (équivalentes à 0,09, 0,9 et 1,3 m/s) en conditions humides ou conditions sèches. Les données obtenues montrent que quelles que soient les conditions d'humidité initiales, les failles simulées montrent toutes un affaiblissement lors du déplacement. Un examen détaillé des microstructures des gouges cisaillées obtenues une fois l'équilibre frictionnel atteint permet de définir deux types de microstructures impliquant deux régimes de déformation : un régime de déformation par roulement avec la formation d'agrégats argileux, et un régime de déformation par glissement avec la formation d'une zone de cisaillement complexe localisée à l'interface gouge-éponte. L'affaiblissement observé lors des expériences semble être lié à une diminution de la proportion de grains roulants par rapport à celle de grains glissants, et semble être favorisé par le développement des agrégats argileux, lesquels sont contrôlés par la teneur en eau.<br /> A partir d'un modèle numérique (P2 FEM) et des données de contrainte cisaillante obtenues lors des essais de friction, il a été possible de calculer l'évolution de la température de la gouge en fonction du déplacement. Les résultats suggèrent que la distance dc pourrait représenter la distance nécessaire à une faille pour produire et diffuser assez de chaleur afin de casser les ponts d'eau capillaire (forces d'adhésion) et ainsi permettre à l'eau contenue dans la gouge d'être libérée. Ce mécanisme est appelé mécanisme d'affaiblissement par drainage.

In reconstruction of on-roadway vehicle accidents, roadway surface gouges and the forces and energy attributed to the related vehicle components become important keys to resolving an accurate accident reconstruction. These roadway gouge forces vary depending upon such factors as surface temperature and the velocity and geometry of the gouging mechanism. Accounting for the forces applied to vehicle components and the energy dissipated from such forces can be helpful in accident reconstruction where supporting data exists. This research documents the force necessary to create a given roadway gouge geometry. Controlled pavement gouging tests were performed using roadway surface temperature and gouging velocity as main factors. The results of this testing and analysis are useful in quantifying gouge forces and energies for use in accident reconstruction. The findings show that the temperature of the roadway surface that is being damaged significantly affects the amount of force required to cause the damage. A summary of experiments and techniques as applied to accident reconstruction are presented.

The majority of faults display a layer of crushed wear material ("fault gouge") between the fault blocks, which influences the strength and stability of faults. This thesis describes the results of a numerical model used to investigate the process of comminution in a sheared granular material. The model, based on the Discrete Element Method, simulates a layer of 2-D circular grains subjected to normal stress and sheared at constant velocity. An existing code was modified to allow grains to break when subjected to stress conditions that generate sufficient internal tensile stresses. A suite of five numerical runs was performed using the same initial system of grains with sizes randomly chosen from a pre-defined Gaussian distribution. A range of confining pressures was explored from 4.5 MPa to 27.0 MPa (in case of quartz grains with average diameter of 1 mm). The average effective friction coefficients of the five simulations were relatively unaffected by comminution and displayed a constant value of about 0.26. The amount of breakage was directly related to both the applied confining pressure and logarithm of the displacement along the fault. The particle size distribution evolved during the runs, but it was apparently determined only by the cumulative number of grain breakage events: two runs with the same number of breakage events had identical particle size distributions, even if they deformed to different extents under different stress conditions. These results suggest that the knowledge of both the local displacement and stress state on a fault can be used to infer the local particle size distribution of the gouge.

No description available.

Clay composition and content profoundly impacts the strength and sealing capacity of a fault zone, reducing frictional resistance to sliding and permeability by as much as 7 orders of magnitude. Previous approaches, including the Shale Gouge Ratio (SGR) and Shale Smear Potential (SSP), have been used to understand and predict the clay content of fault zones. These models are largely limited to mechanical incorporation of detrital clays. This hypothesis stems from field observations of clay gouge and the smearing and associated attenuation of clay-rich shale beds offset by the fault. Recently, diagenesis has been recognized as an additional critical mechanism of clay enrichment In fault zones. My study investigates the relative contributions of both mechanisms of clay enrichment focusing on the implications for fault permeability and strength through structural and elemental mapping of the Moab Fault in Utah. Detailed mapping at Six sites along the Moab Fault in southeast Utah, revealed distinct structural deformation zones as defined by structures and distribution of normally faulted sandstone and shale including: (1) layers of clay-rich gouge separated by slip surfaces that include isolated sandstone breccia; (2) an inner smeared shale adjacent to the gouge showing increasing bed parallel shearing and resulting boudinage closer to the fault, and an outer smear with little shearing but rotation of beds; (3) faulted sandstone hosting deformation bands, slip surfaces, and intersections, joints and veins in locations near relays. Fluid assisted alteration was revealed by a combination of high spatial resolution scan-lines on outcrops element composition and measured sections of measured with a portable X-Ray Fluorescence device. Results to date include: (1) elemental concentrations relative to immobile species (such as Ti) and by structural zone show that Ca, Sr, Rb are preferentially enriched and/or depleted in the fault core, (2) the fault core hosts the greatest alteration; (3) a progressively more extensive and greater density of bed parallel slip surfaces from protolith to gouge where slip surfaces are associated with mixing and disaggregation; (4) stable concentration of elements associated with illite such as K, occurs preferentially in the gouge; (5) localized enrichment and/or depletion reveals solution mass transfer contributed to formation of the fault core and to a lesser extent the damage zones. Elemental mapping clearly demonstrates a compositional evolution of the fault core, and in particular the clay gouge, that cannot be accounted for by mixing of protolithic formations. Thus, observations from elemental mapping show that solution mass transfer influences the formation of clay gouge in the fault zone, in addition to mechanical incorporation of detrital clays from the surrounding protoliths. / Earth and Environmental Science

Die hier präsentierte Studie umfasst detaillierte Untersuchungen zur thermochronologischen, strukturellen sowie morphologischen Entwicklung der Östlichen und Westlichen Sierras Pampeanas in Argentinien, zwischen 26°S to 34°S südlicher Breite. Kapitel 3 diskutiert thermochronologische Daten (Apatit Spaltspuren, Zirkon und Apatit (U-Th)/He) sowie K-Ar Illit-Datierung an Störungsletten aus der Sierra de Comechingones sowie Ar-Ar Alter an Vulkaniten des vulkanischen Gürtels von San Luis (Östliche Sierras Pampeanas). K-Ar Illitalter belegen den Beginn spröder Deformation vor etwa 340 Ma. Thermochronologische Daten dokumentieren geringe Exhumationsraten seit dem späten Paläozoikum sowie eine maximale Exhumierung von etwa 2,3 km seit der späten Kreidezeit. Ar-Ar Datierungen an vulkanischen Gesteinen des San Luis Vulkanischen Gürtels ergeben Alter zwischen 7,54 Ma und 1,91 Ma. Dies belegt ein ostwärts gerichtetes Fortschreiten der magmatischen Front, welches mit einer Verflachung des Subduktionswinkels der Nazca Platte unter die Südamerikanische Platte vor etwa 11.2 Ma assoziiert wird. Darüber hinaus deuten die hier präsentierten thermochronologischen Daten an, dass der Anteil Andiner Exhumation und Hebung an der Gesamthebung und Exhumation der Sierras Pampeanas von geringer ist als gemeinhin angenommen. Kapitel 4 präsentiert Ergebnisse von Niedrig-Temperatur thermochronologischen Untersuchungen sowie K-Ar Alter retrograd gewachsener Illite aus spröden Störungszonen der Sierra de San Luis (Östliche Sierras Pampeanas). K-Ar Illitalter belegen eine lang andauernde Aktivität spröder Deformation welche unmittelbar nach dem Ende der Chanic Phase der Famatinischen Orogenese vor etwa 320 Ma einsetzte und zeitlich mit dem Übergang von duktilen zu spröden Deformationsmechanismen übereinstimmt. Jüngste Illitlater liegen zwischen 222-172 Ma. Diese können als Abkühlalter des Grundgebirges unter die zur Illitbildung benötigten Temperaturen interpretiert werden, jedoch nicht als Ende der spröden Deformation. Diese Interpretation wird von den Ergebnissen thermochronologischer Untersuchungen bestätigt. (U-Th)/He Datierungen an Apatiten und Zirkonen, sowie Apatit Spaltspuranalysen dokumentieren die Exhumation seit dem Perm, welche möglicherweise in Verbindung zur San Rafael Orogenese steht. Die ermittelten Abkühlalter belegen geringe Exhumationsraten sowie die damit einhergehende lange Verweildauer der Proben in den Temperaturbereichen der partial annealing bzw. parial retention zone von Apatit und Zirkon (PRZA, PRZZ und PAZA). Die finale Abkühlung auf Oberflächentemperaturen fand im Verlauf des Jura und der späten Kreide statt. Die Abkühlgeschichten der Sierra de San Luis und Sierra de Comechingones werden in einem Entwicklungsmodel zusammengefasst, welches signifikante Unterschiede in der thermischen Entwicklung beider Gebirgszüge offenbart. Kapitel 5 diskutiert die thermochronologische Entwicklung der Sierra de Pie de Palo, einem ausgeprägten Höhenzug in den Westlichen Sierras Pampeanas. Thermochronologische Untersuchungen zeigen das die strukturelle Entwicklung der Sierra Pie de Palo bereits im späten Paläozoikum einsetzte und von jeher durch tektonisch kontrollierte Erosion geprägt wurde, welche sich im Verlauf des Mesozoikums aufgrund extensionaler Tektonik zwar verlangsamte, jedoch andauerte. Die heutige Topographie des Gebirgszuges bildete sich im Zuge Andiner Kompression im Verlauf des Späten Mesozoikums und Paläogens durch die Hebung und damit einhergehender Denudation einzelner Grundgebirgsblöcke. Die mit der Hebung assoziierte Deformation schritt dabei von Ost nach West voran. Der Gesamtbetrag vertikaler Hebung seit dem frühen Paläozoikum kann auf ca. 3,7-4,3 km eingegrenzt werden, wobei die Gesamtexhumation etwa 1,7-2,2 km bei einer Exhumationsrate von 0,03-0,04 mm/a beträgt. Kapitel 6 stellt eine Methode zur Interpretation von K-Ar Illit Feinfraktionsaltern aus Störungsletten aus nichtsedimentären Gesteinen vor. Gemäß der vorgestellten Methode werden die ermittelten K Ar Illitalter in Kombination mit den Untersuchungsergebnissen unabhängiger Parameter, z.B. Illitkristallinität, Illit-Polytypie und Polytyp-Quantifizierung, Korngröße, Tonmineralogie, K-Ar Abkühlaltern des Nebengesteins sowie mit Ergebnissen thermochronologischer Untersuchungen (AHe, ZHe, AFT) evaluiert. Dieser Interpretationsansatz wird im Rahmen einer regionalen Studie innerhalb der Östlichen Sierras Pampeanas exemplarisch angewandt. Im Zuge dessen wurde eine große Zahl von Störungsletten systematisch beprobt und analysiert. Ermittelte K-Ar Illitalter decken die Zeitspanne vom Devon bis in die Kreidezeit und dokumentieren eine lang anhaltende Phase bruchhafter Deformation in der Region. Alter >320 Ma sind synchron mit einer Periode kompressiver intra-Platten Tektonik, während Permische und Triassische Alter mit einer Periode flacher Subduktion der Farallon Platte unter die Südamerikansche Platte assoziiert werden können. Darüber hinaus belegen die K-Ar Illitalter ein von Nord nach Süd Fortschreiten der spröden Deformation in den Sierras de San Luis und Comechingones. Die Integrität und Konsistenz der analysierten Daten belegt die Leistungsfähigkeit und tektonische Signifikanz der hier vorgestellten Methode, welche somit einen bedeutenden Beitrag zur Entschlüsselung komplexer Abkühlungs- und Deformationsereignisse bieten kann. Jedoch kann gezeigt werden, dass die Aussagekraft der hier vorgestellten Methode stark von der Abkühlgeschichte des Untersuchungsgebietes abhängt. Kapitel 7 präsentiert thermochronologische Daten aus den gesamten Sierras Pampeanas. Darüber hinaus werden alle verfügbaren thermochronologischen und geochronologischen Daten zur Abkühlgeschichte der Sierras Pampeanas diskutiert und in ein Abkühlmodell zusammengefasst. Die Daten belegen eine Abkühlung unter 200°C im Verlauf des Karbons. Im Verlauf des Perms und der Trias schritt die Abkühlung von West nach Ost fort, räumlich und zeitlich einhergehend mit dem fortschreiten eines flachen Subduktionsereignisses der Farallon-Platte unter die heutige Südamerikanische Platte. Mesozoische Riftereignisse und damit einhergehende Sedimentation und Versenkung zeigen nur lokal Einfluss auf die ermittelten Abkühlalter. Dies deutet darauf hin, dass die zum Verlust der Altersinformation der thermochronologischen Systeme notwenige Versenkungstiefen nur entlang der schmalen, räumlich eingeschränkten Kretazischen Riftbecken erreicht werden. Die finale Abkühlung auf Oberflächentemperaturen verlief diachron in den nördlichen und südlichen Sierras Pampeanas. So können im Norden Neogene Alter beobachtet werden, während die südlichen und westlichen Sierras Pampeanas spätestens seit der Kreide bzw. frühen Paleogens auf Oberflächentemperaturen abgekühlt waren. Letzteres deutet auf die Existenz einer positiven Topographie in den südlichen Sierras Pampeanas, bereits vor dem Einsetzen Cenozoischen Andinen Kompression und der im Neogenen einsetzenden flachen Subduktion der Nazca-Platte hin. Dies wiederum wiederspricht der allgemein akzeptierten Hypothese, dass die Exhumation und Hebung der Sierras Pampeanas allein mit der Neogenen flachen Subduktion der Nazca-Platte in Verbindung stehen. Im Gegensatz dazu wird vorgeschlagen, dass diese Neogenen Prozesse lediglich zu einer Überprägung und Akzentuierung des bereits existierenden Reliefs führten. Diese Vermutung kann durch die Berechnung auffallend niedriger Denudationsraten in den Östlichen und Westlichen Sierras Pampeanas von 0,010 0,024 km/a gestützt werden, welche auf stabile Bedingungen, zumindest seit der späten Kreidezeit, hindeuten.

O reparo em dutos defeituosos é previsto por normas e literatura, porém existe grande espaço para definição dos parâmetros ideais para aplicação prática e avaliação do desempenho destes reparos em fadiga. O presente trabalho tem por objetivo a definição dos parâmetros ideais para aplicação de reparos eficientes do tipo dupla calha sem solda circunferencial e com carregamento externo em escala real em dutos com defeitos de mossa com cava. O reparo é baseado na instalação de duas calhas concêntricas ao duto a ser reparado, preenchendo-se o defeito com resina e aplicando carga de compressão através de atuadores hidráulicos com correntes a fim de induzir tensões compressivas na região do defeito e, por fim, as calhas são unidas longitudinalmente pelo processo de soldagem. Para este trabalho, foi realizada uma modelagem numérica utilizando o método de elementos finitos de modo a simular a reprodução do defeito, ensaios de fadiga sem reparo, parâmetros para aplicação do reparo, ensaios de fadiga com reparo e, por fim, ensaio hidrostático. O procedimento proposto foi a reprodução do defeito, primeiramente o duto foi deformado com uma esfera metálica, de modo a formar uma mossa de profundidade igual a 6 % do diâmetro externo e, em seguida, a cava foi usinada com a utilização de um disco abrasivo. Após a produção do defeito, três amostras foram ensaiadas em fadiga, de modo a produzir uma amostra de referência sem reparo a ser comparada com os corpos de prova com reparo. O reparo dupla calha foi aplicado em duas amostras com defeito, sendo essas então submetidas a ensaios de fadiga. Esses ensaios indicaram que ambas as amostras resistiram a um número de ciclos correspondentes a 100 anos de vida em serviço. Por fim, as amostras reparadas após o ensaio de fadiga foram submetidas a ensaios hidrostáticos até a ruptura, a fim de avaliar a vida remanescente. Ambos os dutos romperam fora da região reparada, com uma pressão 2,1 %, menor que a pressão calculada analiticamente. Como principal resultado, foram obtidos parâmetros ideais para aplicação do reparo dupla calha em dutos com defeito tipo mossa com cava. Os resultados experimentais mostram convergência em relação aos dados do modelo numérico, provando que a modelagem por elementos finitos pode ser uma ferramenta útil no desenvolvimento deste tipo de trabalho. / Defective duct repairs are envisaged by norms and by the literature, yet there is enough space left to define ideal parameters for practical application and performance evaluation of these fatigue repairs. This work’s objective is to define the ideal parameters for the application of efficient repairs in double spouts without circumferential welding and real scale external loading in ducts with dent and gouge defects. The repair is based on the installation of two concentric spouts in the duct, filling the defect with resin and applying compression loading through hydraulic actuators with currents to induce compressive stresses in the defective area. Afterwards, the spouts are united lengthwise through the process of welding. To develop this work, we conducted a numerical modelling by using the finite element method to simulate the reproduction of the defect, as well as fatigue tests with no repairs, parameters for the application of repairs, fatigue tests with repairs, and finally a hydrostatic test. The proposed procedure was the reproduction of the defect. At first the duct was deformed with a metallic sphere, to form a dent whose depth was equal to 6 % of the external diameter and, subsequently, the gouge was machined with the help of an abrasive disk. Following the production of a defect, three samples were tested in fatigue to produce a reference sample without repair which would be compared to the samples with repairs. The double spout repair was applied in two samples with defects, which were then subjected to fatigue tests. These tests showed that both samples resisted to a number of cycles corresponding to a 100-year use lifespan. At last, the samples repaired after fatigue tests were subjected to hydrostatic tests until rupture, in order to evaluate their remaining lifespan. Both ducts ruptured outside of the repaired region, with a stress rate of 2.1 %, lower than the stress calculated analytically. The main result of this study was obtaining ideal parameters for the application of double spout repair in ducts with dents and gouge defects. The experimental results show convergence in relation to the numerical model data, proving that finite element modelling can be a useful tool when conducting this kind of work.

Rupture of the Chelungpu fault during the September 21, 1999, 7.6 Mwearthquake in Taiwan caused a 90-Jr,m-long surface rupture with variable displacement along strike. Analysis of core from two holes drilled through the fault zone, combined with geologic mapping and detailed investigation from three outcrops, define the fault geometry and physical properties of the Chelungpu fault in its northern and southern regions. In the northern region, the fault dips 45-60° east parallel to bedding and consists of a narrow (1-20 cm) core of dark-gray, sheared clay gouge at the base of a 30-50 m zone of increased fracture density that is confined asymmetrically to the hanging wall. Microstructural analysis of the fault gouge indicates the presence of extremely narrow clay zones (50-300 μm thick) that are interpreted as the fault rupture surfaces. Few shear indicators are observed outside of the fault gouge, which implies that slip was localized in the gouge in the northern region. Slip localization along a bed-parallel surface resulted in less high-frequency ground motion and larger displacements during the earthquake than in the southern region. Observations from the southern region indicate that the fault dips 20-30° at the surface and consists of a wide (20- 70 m-thick) zone of sheared, foliated shale with numerous gouge zones. A footwall-ramp geometry juxtaposes 2000-3000 m of flat-lying Quaternary Toukoshan Formation in the footwall with Pliocene and Miocene, east-dipping siltstone and muds tone in the hanging wall. The wide, diffuse fault zone contributed to the lower displacement and higher frequency ground motion in the southern region during the 1999 earthquake. The structure in the northern region is the result of the fault being a very young (<50 >ka) fault segment in the hanging wall of an older segment of the Chelungpu fault, buried in the Taichung basin. The fault in the southern region is located on an older (~1 Ma) fault trace. The contrasting fault properties in the different regions are responsible for the variability in strong-motion and displacement observed during the 1999 earthquake.