Major Earthquake Events Research Articles

Ground improvement methods for liquefaction remediation

Soil liquefaction continues to be a major source of damage to buildings and infrastructure after major earthquake events. Ground improvement methods are widely used at many sites worldwide as a way of mitigating liquefaction damage. The relative success of these ground improvement methods in preventing damage after a liquefaction event and the mechanisms by which they can mitigate liquefaction continue to be areas of active research. In this paper the emphasis is on the use of dynamic centrifuge modelling as a tool to investigate the effectiveness of ground improvement methods in mitigating liquefaction risk. Three different ground improvement methods will be considered. First, the effectiveness of in situ densification as a liquefaction resistance measure will be investigated. It will be shown that the mechanism by which soil densification offers mitigation of the liquefaction risk can be studied at a fundamental level using dynamic centrifuge modelling. Second, the use of drains to relieve excess pore pressures generated during an earthquake event will be considered. It will be shown that current design methods can be further improved by incorporating the understanding obtained from dynamic centrifuge tests. Finally, the use of soil grouting to mitigate liquefaction risk will be investigated. It will be shown that by grouting the foundation soil, the settlement of a building can be reduced following earthquake loading. However, the grouting depth must extend the whole depth of the liquefiable layer to achieve this reduction in settlements. La liquéfaction des sols est toujours une des principales causes d'endommagement de bâtiments et d'infrastructures à la suite de tremblements de terre de forte intensité. Des méthodes de renforcement du terrain sont répandues dans de nombreuses régions du monde pour mitiger les dommages provoqués par le liquéfaction. Le succès relatif remporté par ces méthodes de renforcement du terrain dans la prévention des dégâts à la suite d'un évé nement avec liquéfaction, ainsi que les mécanismes leur permettant de mitiger la liquéfaction, sont toujours les sujets d'une recherche active. Dans la présente communication, nous mettons l'accent sur l'utilisation de la modélisation centrifuge dynamique en tant qu'outil dans la recherche sur l'efficacité des méthodes de renforcement du terrain pour la mitigation des risques de liqué faction. On se penche sur trois méthodes diverses d'optimisation du sol. Premièrement, on examine l'efficacité de la densification in situ comme mesure de la résistance à la liquefaction. Deuxièmement, on examine l'emploi de drains pour réduire l'excès de pression des pores produite au cours d'un tremblement de terre. On démontrera qu'il est possible de perfectionner les méthodes d'étude actuelles en incorporant les enseignements des tests centrifuges dynamiques. Enfin, on examine l'utilisation du scellement des fondations pour la mitigation des risques de liquéfaction, et on démontre qu'en scellant le son des fondations, on parvient à réduire l'affaissement d'un bâtiment à la suite des contraintes appliqué es par le tremblement de terre. Toutefois, pour réaliser cette réduction de l'affaissement, la profondeur de scellement doit âtre égale à celle de la l'intégralité de la couche liquéfiable.

Effect of soil conditions on the response of reinforced concrete tall structures to near‐fault earthquakes

AbstractCharacteristics of near‐fault earthquakes (NFE) are particularly different from that of the far‐field ones. Far‐field ground motions are characterized by low peak ground acceleration (PGA) and high frequency, whereas near‐fault ground motions have a high peak ground velocity (PGV) and long period pulse. Several recent earthquakes, e.g. 1992 Landers, 1994 Northridge, 1995 Kobe, and 1999 Chichi earthquake events, have caused substantial damage to near‐fault flexible structures. The nonlinear dynamic behaviour of tall reinforced concrete (RC) frame structures subjected to NFE records is influenced by the characteristics of the foundation soil. The assumption of a fixed‐base model for this type of structure might not adequately represent their seismic response. Therefore, the seismic performance evaluation analysis should take into account the soil–structure interaction (SSI). In this study, the seismic performance of a 20‐storey and a 6‐storey RC frame structures with fixed‐base and flexible‐base conditions is evaluated. The characteristics of the flexible‐base models cover four types of soils, namely, soft soil, medium soil, stiff soil and a rock soil, as classified by the International Building Code. A set of 13 near‐fault acceleration time histories recorded on the four types of soil from major earthquake events is selected for the analysis. Three criteria for scaling the records were considered, namely, same maximum spectral acceleration, same spectral acceleration at fundamental period of fixed‐base model, and same spectral acceleration at fundamental period of flexible‐base model. The analysis evaluates the effect of SSI on the dynamic behaviour by comparing the response of the flexible‐base model to the fixed‐base model of the structure when subjected to different earthquake records on a specific soil type. It is concluded that SSI effects could vary significantly according to the characteristics of the NFE record, the scaling criterion and the seismic performance indicator representing the SSI. This observation is valid for tall and low‐rise structures. Copyright © 2007 John Wiley & Sons, Ltd.

U-series dating and geochemical tracing of late Quaternary travertine in co-seismic fissures

We present a method to constrain the timing of fissure generation related to late Quaternary seismic events using the uranium-series technique. Dated samples were from travertine deposits precipitated in co-seismic extensional fissures along major active faults in Western Turkey. Stable isotope and REE data indicate that the precipitation of the fissure travertines was not controlled by the hydrologic regime that is responsible for the speolethem deposition in the same region. Moreover, the REE composition and concentration of the water from which the fissure travertine precipitated were significantly different from those of the current geothermal waters in the study area. The carbonate generation in the co-seismic fissures is interpreted to be the product of rapid precipitation from deeply infiltrated and CO 2-enriched surface water during seismic strain cycles. Results show that U-series dating of fracture-filling travertine deposits from seismically active areas provide important temporal information relevant to establishing recurrence intervals of late Quaternary and prehistoric major earthquake events. Precise dating of prehistoric earthquakes may be of great value for seismic hazard studies and earthquake forecasting research, for which accurate estimates of recurrence intervals are critical.

Dating and geochemical tracing of paleoseismic events

Dating of shallow faults is crucial to understanding of the mechanism of earthquake generation and future seismic risk. However, radiometric dating of low temperature authigenic minerals in shallow fault zones has been a major challenge because of the contamination of fault rocks by older mineral phases and the overprinting of the syn-tectonic isotopic signature by post-tectonic re-crystallisation events. We present a technique for a reliable dating of fault movements using a combined application of low temperature geochronology, mineralogy and isotope-trace element geochemistry. Such combined studies further allow constraining the origin and migration of seismically mobilised fluids along active fault zones. We investigated illitic clay minerals from fault gouges and late Quaternary carbonate deposits in co-seismic fissures along currently active fault zones in Turkey. Our results indicate that the North Anatolian Fault Zone has been active since the Late Paleocene ? Early Eocene that followed immediately the continental collision related to the closure of the Neotethys Ocean. Fault movement is considered to have driven deeply sourced fluids, with metamorphic fluids being supplied by the compression along the Neotethyan orogenic suture zone. Precise dating of the late Quaternary carbonate deposits by U-series geochronology provide important constraints on the late Quaternary fissure generation related to the neotectonic processes and active faulting. Isotopic and trace element data indicate that the fissure carbonate deposits precipitated from deeply hydrothermal fluids. Mobilisation of deep fluids and their surface effusion is attributed to tectonic processes such as seismic pumping. K-Ar and U-series dating of clay and carbonate minerals respectively in seismically active areas is very promising for further studies for dating of major earthquake events and their recurrent intervals, with significant implications for the Australian active fault systems.

Emergency storage project: Design and construction of the Lake Hodges to Olivenhain Tunnel Pipeline, San Diego, California

The Lake Hodges to Olivenhain Tunnel Pipeline (LHOP) Project is part of a 40 megawatt pumped storage project, which is a component of the San Diego Water Authority's Emergency Storage Project. The project, located in the arid southwest of USA and earthquake country, is a design-build engineering and construction effort for a pressure tunnel extending from the Olivenhain Dam Reservoir to Lake Hodges. The project takes economic advantage of two reservoirs to generate electricity during peak energy demands as well as provide a reliable source of water during periods of drought or a major earthquake event. The project represents innovative planning, design, and construction for underground space use and construction whilst using conventional construction techniques and offering unique insight, cost effectiveness, and safety considerations to the design-build process for underground works in the USA. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.

Base isolation of an existing 10-storey building to enhance earthquake resistance

The Rankine Brown Building at Victoria University of Wellington, New Zealand houses the University Library and is pivotal to the operation of the University. Built in the early 1960s, the building was of innovative form and construction for its time, with long span precast concrete waffle slabs over 10 floors supported on 16 main columns. Three years ago a review of the building structure suggested that increased protection of the building would be required to meet the University's expectation for operational continuity after a moderate or major earthquake event in the Wellington area. This paper outlines:
 Probable areas of structural yielding in a major earthquake event.
 Structural analysis for base isolation using earthquake time history records.
 Details of base isolation bearings.
 Installation of the base isolation bearings.
 Other structural details that allow movement of the superstructure to take place due to base isolation.

A seismic upgrading method for steel arch bridges using buckling‐restrained braces

AbstractIn this study the employment of buckling‐restrained braces (BRBs) as energy dissipation dampers is attempted for seismic performance upgrading of steel arch bridges and the effectiveness of BRBs to protect structures against strong earthquakes is numerically studied. With buckling restrained, BRB members can provide stable energy dissipation capacity and thus damage of the whole structure under major earthquakes can be mitigated. Cyclic behaviour of such members is addressed with a numerical simulation model, and a strength design method for BRBs is proposed. BRBs are then placed at certain locations on the example steel arch bridge to replace some normal members with two schemes, and the effect of the two installation schemes of BRBs for seismic upgrading is investigated by non‐linear time‐history analyses under various ground motions representing major earthquake events. Compared with the seismic behaviour of the original structure without BRBs, satisfactory seismic performance is seen in the upgraded models, which clarifies the effectiveness of the proposed upgrading method and it can serve as an efficient solution for earthquake‐resistant new designs and retrofit of existing steel arch bridges. Copyright © 2005 John Wiley & Sons, Ltd.

Correlation of JMA instrumental seismic intensity with strong motion parameters

AbstractThe Japan Meteorological Agency (JMA) seismic intensity (IJMA) has been used as a measure of strong shaking for many years in Japan, and it necessitates to know the correlation between the JMA seismic intensity and other strong motion indices, e.g. Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), and Spectrum Intensity (SI). In this study, two strong motion data sets were selected; in which, the first set consists of 879 three‐components non‐liquefied records selected from 13 major earthquake events that occurred in Japan, the United States, and Taiwan, and the second set consists of 17 liquefied records selected from 7 major earthquake events that occurred in Japan and the United States. The JMA seismic intensity and other ground motion indices were calculated using the selected data sets. The relationships between the JMA seismic intensity and PGA, PGV, and SI were then derived performing a two‐stage linear regression analysis. Results from the analysis show that the JMA instrumental seismic intensity shows higher correlation with SI than PGA or PGV, and it shows the highest correlation with the parameters such as the combination of PGA and SI or the product of PGA and SI. The obtained relationships are also compared with the ones obtained by other studies, which may be useful for the disaster management agencies in Japan and deployment of new SI‐sensors that monitor both PGA and SI. Copyright © 2002 John Wiley & Sons, Ltd.

A chronology of natural and anthropogenic influences on coastal sedimentation, New Zealand

14C and 137Cs chronologies of sediment accumulation were obtained from five sediment cores taken from Wellington Harbour, New Zealand. A 10,000-year chronology records the Holocene transgression, European colonisation, and variations in the general sediment accumulation rate caused by earthquake uplift and anthropogenic activity. Rates vary from a high of ~ 60 to a low of 0.1 mm a−1. In general, rates increased at the beginning of the Holocene marine transgression, but by ~ 5000 yr BP they reached a stable level. Harbour-wide, these rates remained stable until the second half of the 19th Century when deforestation by European settlers caused order of magnitude increases in sediment accumulation. In the past 40–80 years rates have increased again as a result of urban growth and river channel management, although the effects are less pervasive. Harbour-wide influences can be placed in two categories, natural and anthropogenic, the latter being recent contributions to a sedimentary regime dominated by the Holocene marine transgression.Sediment accumulation rates indicate that two major earthquake uplift events had only a local effect on harbour sediments. Anthropogenic influences are considered to be more significant sedimentologically than earthquake activity.

北部フォッサマグマ地域の地震活動特性

The geologic feature of the northern Fossa Magna region is characterized by a well developed folded belt system. Recent microseismicity over 10 years and historic earthquakes reveal that there are seismic zones pararell to the axes of this structure: Itoigawa-Shizuoka Tectonic Line, the western side of Shinano River, the western margin of the Central Belt of Uplift, and the eastern margin of the Central Belt of Uplift. The last zone was recently recognized by the earthquake sequence with the main shock of M 4.9 in 1986. The fcal mechanism solutions and other geologic and geodetic evidence indicate the region is compressed in the direction perpendicular to the folded belts. We can also find seismic activity lines perpendicular to or oblique to these folding axes: the Chikumagawa Tectonic Line separates the Central Belt of Uplift with a left lateral offset of 10km; the seismic line along the eastern side of the volcanic line of Myoko-san, Kurohime-yama and Iizuna-yama makes the eastern edge of the seismic gap around the northern end of the Itoigawa-Shizuoka Line.A 20-25 years recurrence time is found in the occurrence of the major earthquake events in the central part of the northern Fossa Magna in recent 140 years.Seismic active regions are grouped into some rectangular blocks with their bases being either pararell or perpendicular to the folded belts. The activity in a block became active nearly simultaneously, and it sometimes migrated to other blocks with some delay time. The high activity migrated from the block region around the Chikumagawa Tectonic Line to both the northern activity block around the Japan Sea coast and the active region in the southern Fossa Magna during the period from 1986 to 1987.The migration of the seismic activity along the Fossa Magna region may be due to delayed transmission of the stress field in the viscoelastic or elastoviscous medium. The exponential time dependence of the decay rate of the Matsushiro swarm activity for a long period more than 20 years since 1965 is found to be reasonably interpreted by the relaxation process of stresses within the elastoviscous medium. The viscosity changed from 1.1×1019 poise to 2.7×1020 poise as time elapsed. The first value is comparable with that of a ground surface rock body estimated by secular ground tilts and strains. The latter is the same order of the values obtained in the long period second creep experiments using granite and gabbro. The Matsushiro region is one of the region where the viscosity might have been very low due to numerous micro-cracks.