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To construct and test certain hypotheses of earthquake occurrence, we’ve compiled a new catalog covering the whole of California, which lists all known earthquakes at magnitude 4.7 and above and provides focal mechanism informati...
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To construct and test certain hypotheses of earthquake occurrence, we’ve compiled a new catalog covering the whole of California, which lists all known earthquakes at magnitude 4.7 and above and provides focal mechanism information for each earthquake. Accounting for magnitude errors, the catalog should be complete at magnitude 5.0 and above for most of California after 1940 and at specified higher thresholds otherwise.
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The fundamental objective of earthquake engineering is to protect lives and livelihoods through the reduction of seismic risk. Directly or indirectly, this generally requires quantification of the risk, for which quantification of...
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The fundamental objective of earthquake engineering is to protect lives and livelihoods through the reduction of seismic risk. Directly or indirectly, this generally requires quantification of the risk, for which quantification of the seismic hazard is required as a basic input. Over the last several decades, the practice of seismic hazard analysis has evolved enormously, firstly with the introduction of a rational framework for handling the apparent randomness in earthquake processes, which also enabled risk assessments to consider both the severity and likelihood of earthquake effects. The next major evolutionary step was the identification of epistemic uncertainties related to incomplete knowledge, and the formulation of frameworks for both their quantification and their incorporation into hazard assessments. Despite these advances in the practice of seismic hazard analysis, it is not uncommon for the acceptance of seismic hazard estimates to be hindered by invalid comparisons, resistance to new information that challenges prevailing views, and attachment to previous estimates of the hazard. The challenge of achieving impartial acceptance of seismic hazard and risk estimates becomes even more acute in the case of earthquakes attributed to human activities. A more rational evaluation of seismic hazard and risk due to induced earthquakes may be facilitated by adopting, with appropriate adaptations, the advances in risk quantification and risk mitigation developed for natural seismicity. While such practices may provide an impartial starting point for decision making regarding risk mitigation measures, the most promising avenue to achieve broad societal acceptance of the risks associated with induced earthquakes is through effective regulation, which needs to be transparent, independent, and informed by risk considerations based on both sound seismological science and reliable earthquake engineering.
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The work of John Milne, the centenary of whose death is marked in 2013, has had a large impact in the development in global seismology. On his return from Japan to England in 1895, he established for the first time a global earthq...
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The work of John Milne, the centenary of whose death is marked in 2013, has had a large impact in the development in global seismology. On his return from Japan to England in 1895, he established for the first time a global earthquake recording network, centred on his observatory at Shide, Isle of Wight. His composite bulletins, the "Shide Circulars" developed, in the twentieth century, into the world earthquake bulletins of the International Seismological Summary and eventually the International Seismological Centre, which continues to publish the definitive earthquake parameters of world earthquakes on a monthly basis. In fact, seismology has a long tradition in Britain, stretching back to early investigations by members of the Royal Society after 1660. Investigations in Scotland in the early 1840s led to a number of firsts, including the first network of instruments, the first seismic bulletin, and indeed, the first use of the word "seismometer", from which words like "seismology" are a back-formation. This paper will present a chronological survey of the development of seismology in the British Isles, from the first written observations of local earthquakes in the seventh century, and the first theoretical writing on earthquakes in the twelfth century, up to the monitoring of earthquakes in Britain in the present day.
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Current code procedures for stress and stability analysis of new and existing concrete-gravity dams are primarily based on conventional methods of analysis. Such methods can be applied in a straightforward manner but there has bee...
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Current code procedures for stress and stability analysis of new and existing concrete-gravity dams are primarily based on conventional methods of analysis. Such methods can be applied in a straightforward manner but there has been evidence that they may be inaccurate or, possibly, not conservative. This paper presents finite element modeling and analysis procedures and makes recommendations for local failure criteria at the dam-rock interface aimed at predicting more accurately the behavior of dams under hydraulic and anchoring loads.
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This paper will look at what we have and have not achieved in reducing the risk to human life from earthquakes in the last 50 years. It will review how success has been achieved in a few parts of the world, and consider what needs...
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This paper will look at what we have and have not achieved in reducing the risk to human life from earthquakes in the last 50 years. It will review how success has been achieved in a few parts of the world, and consider what needs to be done by the scientific and engineering community globally to assist in the future task of bringing earthquake risks under control. The first part of the talk will re-examine what we know about the casualties from earthquakes in the last 50 years. Almost 80% of about I million deaths turn out to have been caused by just ten great earthquakes, together affecting a tiny proportion of the territory at risk from heavy ground shaking. The disparity between richer and poorer countries is also evident, not only in fatality rates, but also in their rates of change. But the existing casualty database turns out to be a very poor basis for observing such differences, not only because of the small number of lethal events, but also because of the very limited data on causes of death, types and causes of injury. These have been examined in detail in only a few, recent events. All that can be said with certainty is that a few wealthier earthquake-prone countries or regions have made impressive progress in reducing the risk of death from earthquakes, while most of the rest of the world has achieved comparatively little, and in some areas the problem has become much worse. The second part of the paper looks in more detail at what has been achieved country by country. Based on a new expert-group survey of key individuals involved in earthquake risk mitigation, it will examine what are perceived to be the successes and failures of risk mitigation in each country or group of countries. This survey will be used to highlight the achievements of those countries which have successfully tackled their earthquake risk; it will examine the processes of earthquake risk mitigation, from campaigning to retrofitting, and it will consider to what extent the achievement is the result of affluence, scientific and technical activity, political advocacy, public awareness, or the experience of destructive events. It will ask to what extent the approaches pioneered by the global leaders can be adopted by the rest. The final section of the talk will argue that it can be useful to view earthquake protection activity as a public health matter to be advanced in a manner similar to globally successful disease-control measures: it will be argued that the key components of such programmes-building in protection; harnessing new technology and creating a safety culture-must be the key components of earthquake protection strategies also. It will consider the contribution which the scientific and engineering community can make to bringing down today's unacceptably high global earthquake risk. It will be suggested that this role is wider than commonly understood and needs to include: Building-in protection Improving and simplifying information available for designers and self-builders of homes and infrastructure. Devising and running "building for safety" programmes to support local builders. Harnessing new technologies Developing and testing cost-effective techniques for new construction and retrofit. Creating a safety culture Involvement in raising public awareness. Political advocacy to support new legislation and other actions. Prioritising action on public buildings, especially schools and hospitals. Examples of some of these actions will be given. International collaboration is essential to ensure that the resources and expertise available in the richer countries is shared with those most in need of help. And perhaps the most important single task for the engineering community is to counter the widespread fatalistic attitude that future earthquakes are bound to be at least as destructive as those of the past.
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The data of pre-seismic subsurface fluid anomalies of such earthquakes as Datong-Yanggao M_s 6.1 event on Oct. 19, 1989, western Baotou M_s 6.4 event on May 3, 1996 and Zhangbei- Shangyi M_s 6.2 event on Jan. 10, 1998 are systemat...
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The data of pre-seismic subsurface fluid anomalies of such earthquakes as Datong-Yanggao M_s 6.1 event on Oct. 19, 1989, western Baotou M_s 6.4 event on May 3, 1996 and Zhangbei- Shangyi M_s 6.2 event on Jan. 10, 1998 are systematically collected and arranged. Then the Features of patterns, spatial distribution, time variation and time-spatial evolution of these Anomalies are compared and comprehensively analyzed. Then the formation and evolution Mechanism of medium- and short-term anomaly field of subsurface fluids in the northern North China area is proposed.
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The Indian subcontinent has suffered some of the greatest earthquakes in the world. The earthquakes of the late nineteenth and early twentieth centuries triggered a number of early advances in science and engineering related to ea...
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The Indian subcontinent has suffered some of the greatest earthquakes in the world. The earthquakes of the late nineteenth and early twentieth centuries triggered a number of early advances in science and engineering related to earthquakes that are discussed here. These include the development of early codes and earthquake-resistant housing after the 1935 Quetta earthquake in Baluchistan, and strengthening techniques implemented after the 1941 Andaman Islands earthquake, discovered by the author in remote islands of India. Activities in the late 1950s to institutionalize earthquake engineering in the country are also discussed. Despite these early developments towards seismic safety, moderate earthquakes in India continue to cause thousands of deaths, indicating the poor seismic resilience of the built environment. The Bhuj earthquake of 2001 highlighted a striking disregard for structural design principles and quality of construction. This earthquake was the first instance of an earthquake causing collapses of modern multi-storey buildings in India, and it triggered unprecedented awareness amongst professionals, academics and the general public. The earthquake led to the further development of the National Information Centre of Earthquake Engineering and the establishment of a comprehensive 4-year National Programme on Earthquake Engineering Education that was carried out by the seven Indian Institutes of Technology and the Indian Institute of Science. Earthquake engineering is a highly context-specific discipline and there are many engineering problems where appropriate solutions need to be found locally. Confined masonry construction is one such building typology that the author has been championing for the subcontinent. Development of the student hostels and staff and faculty housing on the new 400-acre campus of the Indian Institute of Technology Gandhinagar has provided an opportunity to adopt this construction typology on a large scale, and is addressed in the monograph. The vulnerability of the building stock in India is also evident from the occasional news reports of collapses of buildings under construction or during rains (without any earthquake shaking). Given India's aspirations to be counted as one of the world's prosperous countries, there is a great urgency to address the safety of our built environment. There is a need: to create a more professional environment for safe construction, including a system for code enforcement and building inspection; for competence-based licensing of civil and structural engineers; for training and education of all stakeholders in the construction chain; to build a research and development culture for seismic safety; to encourage champions of seismic safety; to effectively use windows of opportunity provided by damaging earthquakes; to focus on new construction as opposed to retrofitting existing buildings; and to frame the problem in the broader context of overall building safety rather than the specific context of earthquakes. Sustained long-term efforts are required to address this multi-faceted complex problem of great importance to the future development of India. While the context of this paper is India, many of the observations may be valid and useful for other earthquake-prone countries.
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The following is a very brief precis of the procedures, both computa-tional and otherwise, which are used to produce the Bulletin. Both preliminary estimates of earthquake foci and observational dataare collected in computer-reada...
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The following is a very brief precis of the procedures, both computa-tional and otherwise, which are used to produce the Bulletin. Both preliminary estimates of earthquake foci and observational dataare collected in computer-readable form on such media as magnetictapes, punched cards and punched paper tape as well as in the form ofcoded data sheets and station bulletins, the latter being converted intocomputer-readable form at the Centre. These data are entered into acombination disc-magnetic tape storage system as soon as possibleafter receipt. When a month's data are to be processed, the relevantestimates and observations are arranged in chronological order and therevision process begins.
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The seismic response of pile foundations is a very complex process involving inertial interaction between structure and pile foundation, kinematic interaction between piles and soils, seismically induced pore-water pressures (PWP)...
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The seismic response of pile foundations is a very complex process involving inertial interaction between structure and pile foundation, kinematic interaction between piles and soils, seismically induced pore-water pressures (PWP) and the non-linear response of soils to strong earthquake motions. In contrast, very simple pseudo-static methods are used in engineering practice to determine response parameters for design. These methods neglect several of the factors cited above that can strongly affect pile response. Also soil–pile interaction is modelled using either linear or non-linear springs in a Winkler computational model for pile response. The reliability of this constitutive model has been questioned. In the case of pile groups, the Winkler model for analysis of a single pile is adjusted in various ways by empirical factors to yield a computational model for group response. Can the results of such a simplified analysis be adequate for design in all situations? The lecture will present a critical evaluation of general engineering practice for estimating the response of pile foundations in liquefiable and non-liquefiable soils during earthquakes. The evaluation is part of a major research study on the seismic design of pile foundations sponsored by a Japanese construction company with interests in performance based design and the seismic response of piles in reclaimed land. The evaluation of practice is based on results from field tests, centrifuge tests on model piles and comprehensive non-linear dynamic analyses of pile foundations consisting of both single piles and pile groups. Studies of particular aspects of pile–soil interaction were made. Piles in layered liquefiable soils were analysed in detail as case histories show that these conditions increase the seismic demand on pile foundations. These studies demonstrate the importance of kinematic interaction, usually neglected in simple pseudo-static methods. Recent developments in designing piles to resist lateral spreading of the ground after liquefaction are presented. A comprehensive study of the evaluation of pile cap stiffness coefficients was undertaken and a reliable method of selecting the single value stiffnesses demanded by mainstream commercial structural software was developed. Some other important findings from the study are: the relative effects of inertial and kinematic interactions between foundation and soil on acceleration and displacement spectra of the super-structure; a method for estimating whether inertial interaction is likely to be important or not in a given situation and so when a structure may be treated as a fixed based structure for estimating inertial loads; the occurrence of large kinematic moments when a liquefied layer or naturally occurring soft layer is sandwiched between two hard layers; and the role of rotational stiffness in controlling pile head displacements, especially in liquefiable soils. The lecture concludes with some recommendations for practice that recognize that design, especially preliminary design, will always be based on simplified procedures.
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The paper presents a comprehensive review on shear strength provisions of RC beam-column joint in various national codes viz. ACI 318-2014, NZS 3101-1:2006, EN 1998-1:2004, CSA A23.3:2004, AIJ:2010, and IS 13920:2016. The shear st...
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The paper presents a comprehensive review on shear strength provisions of RC beam-column joint in various national codes viz. ACI 318-2014, NZS 3101-1:2006, EN 1998-1:2004, CSA A23.3:2004, AIJ:2010, and IS 13920:2016. The shear strength equation given in these codes are generic and simple in application, which is based on the contribution of only a few governing parameters. However, the effects of governing parameters in different codes are considered in different ways. As a result, the code prediction varies significantly among themselves as well as with experimental studies. Considering these differences, the influence of various governing parameters on the joint shear strength are evaluated. A database is compiled from 492 experimental results of beam-column joints from literature. To find the cause of variation between code prediction and experimental observations, different type of failure modes of beam-column joints is studied. Consequently, two parameters namely, aspect ratio of joint and area ratio of column to beam cross-section is observed to be affecting the code predictions considerably. The influence of these two parameters on the joint shear strength is validated with the compiled experimental results. Therefore, to ameliorate the code prediction, two approaches i.e. aspect ratio approach and area ratio approach are proposed. The first approach is based on the effect of variation of strut angle on joint shear strength, whereas, the second approach proposes various empirical modification factors based on area ratio of column to beam cross-section. By using these two approaches, it is observed that the difference between the code predictions and experimental results can be minimized considerably. These approaches make the code prediction suitable for design purpose.
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