Strong Earthquake Ground Shaking Research Articles

A review on improved construction methods for clay-brick and concrete-block ordinary masonry buildings

ABSTRACT Masonry construction is the leading construction method for building constructions worldwide. Despite their relatively poor seismic performance, masonry buildings have widespread appeal owing to their low construction costs and ease of construction especially in rural and semi-urban centres of developing countries like India. In the recent past, however, innovative techniques in masonry constructions have significantly improved the seismic behaviour of low and medium rise masonry buildings and have satisfactorily performed under strong earthquake ground shaking. This paper critically summarizes the different seismically-improved construction methods for clay-brick and concrete-block ordinary masonry buildings adopted worldwide. While the same method may be applied in different regions of the world, the use of different types of masonry units, however, do not necessarily yield the same results. For regions where the first use of a seismically-improved construction method is contemplated, there is a need to further investigate the efficacy of any method with the locally available materials of the region for economic feasibility and social acceptance of the proposed method.

Detecting pre-eruptive magmatic processes of the 2018 eruption at Kilauea, Hawaii volcano with ambient noise interferometry

A sequence of eruptions in the lower East Rift Zone (LERZ) of the Kilauea, Hawaii volcano commenced in early May 2018 and caused serious damage and residential evacuation. The post-eruption drainage and collapses of the summit lava lake and caldera suggest a well-connected magmatic plumbing system along the rift zone. How and when the pre-eruptive magmatic processes in such connecting system occurred are, however, still unclear. For that, we apply ambient noise interferometry with seismic data from January 2017 to June 2018 from 12 broadband seismometers to investigate spatiotemporal seismic velocity changes (dv/v) of the upper crust in the Kilauea area. The dv/v variations in three frequency bands (0.3–0.6 Hz, 0.6–0.9 Hz, and 0.9–2.0 Hz) show distinct responses to strong earthquake ground shaking and deep magmatic intrusion processes. Earthquake-induced dv/v drops mainly in the higher two frequency bands imply shallow mechanical changes within the uppermost 1 km of the crust. In contrast, the magma-related dv/v changes can be characterized into three periods of activity: from the December 2017 to March 15, 2018, a dv/v excursion only seen in the lowest frequency band indicates the magmatic intrusion processes taking place at the depth range of 1–4 km, consistent with the proposed depth of the magma reservoir-dike system in the rift zone. The spatial dv/v distribution suggests that the magma may intrude to the deeper summit magma reservoir and in the upper East Rift Zone (UERZ) at this time. From March 15 to April 17 in 2018, the summit inflation recorded by tiltmeters causes the dv/v increases in the higher two frequency bands. After April 17 to the eruption, the accumulating damage of the edifice together with the stronger intrusion activity in the UERZ result in dv/v decreases in all three frequency bands around the summit and UERZ areas. Our observations highlight that the ambient noise interferometry analysis provides an opportunity to image and understand the pre-eruptive processes of reservoir-dike magma system and could be a useful supplement to current volcanic monitoring systems.

The 2011 Tohoku-oki tsunami — Three years on

Abstract The 2011 Tohoku-oki tsunami that devastated the Pacific coast of Tohoku, Japan was a turning point for modern research. As a result of this event it was recognized that paleotsunami research is vital to help understand the size and recurrence interval of low-frequency large tsunamis. This paper reviews the progress of geological research on the 2011 Tohoku-oki tsunami and summarizes new questions that are arising out of this work. For example, recent work suggests that the landward extent and thickness of the sandy deposit, as well as the presence or absence of marine microfossils in the sediment are most likely to be mainly controlled by the initial wave properties, sediment source, offshore bathymetry and onshore topography. This in turn implies that there are certain relationships between the characteristics of a tsunami deposit and the wave properties and it may be possible to reconstruct the latter from the deposits. Offshore tsunami deposits related to the 2011 Tohoku-oki tsunami have also been well described. This recent research indicates that sedimentation and erosion in inner bay and open ocean (~ 20 m water depth) locations can be in the order of several meters, suggesting that the tsunami shear force was strong in the nearshore zone. On the other hand, sandy to muddy deposits a few centimeters thick were observed at about 100 to 6000 m water depth. It is likely that the tsunami resulted in resuspension of sea bottom sediments and that suspended material flowed downslope as a turbidity current or suspended flow, although many authors recognize the possibility that strong earthquake groundshaking might have also generated turbidity currents. Studies of the 2011 Tohoku-oki event have led researchers back to two of the fundamental issues of tsunami geology: understanding the linkage between onshore and offshore sedimentation and erosion, and establishing identification criteria for tsunami deposits. Moreover though, beyond the issue of simple tsunami geology, it is important for all researchers to communicate with governments and the general public in order to reduce future casualties by using risk assessments based on our understanding of infrequent large tsunamis.

Multisource, High-resolution Seismic-reflection Imaging of Meeman-Shelby Fault and a Possible Tectonic Model for a Joiner Ridge-Manila High Stepover Structure in the Upper Mississippi Embayment Region

Other than the Crittenden County fault zone (CCFZ), little is known about the seismic hazard from faults within 50 km of Memphis, Tennessee, a city that contains a large inventory of older buildings that are vulnerable to moderate and strong earthquake ground shaking. To address this lack of knowledge, reconnaissance high-resolution seismic-reflection surveys using Mini-Sosie (Williams et al. 2001) and both P - and S -wave hammer sources (this study) were acquired at the boundary between the loess-covered bluffs (upland area) and the modern Mississippi River floodplain in Meeman-Shelby Forest State Park about 25 km north of Memphis (Figures 1A and 1B). Williams et al. (2001) interpreted a previously unknown fault beneath the floodplain, termed the Meeman-Shelby fault (MSF). Because the focus of the Mini-Sosie survey was to image deeper reflections in the 90–1,000 m depth range, this profile did not image shallower alluvium horizons such as the base of the Quaternary (Pliocene-Pleistocene), a boundary that can generate a strong reflection in this area ( e.g. , Crone 1992; Luzietti et al. 1992). Deformation of the Pliocene-Pleistocene boundary is also important for assessing fault activity in the embayment. Based upon the Williams et al. (2001) results, a higher-resolution 1.5-km hammer-source P -wave profile and a 1.1-km S -wave profile were acquired to assess Quaternary MSF deformation (Figure 1B). We describe two separate results from the combined analysis of the Mini-Sosie and hammer profiles. First, we describe stratigraphic information obtained from the P - and S -wave hammer surveys, which were acquired across the fault imaged in the Mini-Sosie profile. These two hammer profiles constrain the fault trace to near-vertical (80°), projecting to the surface just east of the profiles. The profiles also image both Pleistocene and Holocene floodplain deposits. Using the velocity data obtained from the S -wave profile, …

Dynamic Shear and Axial-Load Failure of Reinforced Concrete Columns

Reinforced concrete columns with light transverse reinforcement may be susceptible to shear and subsequent axial-load failures during strong earthquake ground shaking. An experimental program examined the behavior of two half-scale, one-story frames with axial loads representative of those expected for the lower story of a multistory building. The frames were subjected to unidirectional simulated earthquake motion applied at the base. Shear failures of an interior column led to axial-load failure and redistribution of internal forces to adjacent framing components. Recorded data illustrated the details of the shear and axial failures and the redistribution to adjacent components. This paper discusses the global response of the frames and the shear and axial-load response of the shear-critical interior column.

Time-delayed control design for active control of structures: principles and applications

In this paper we develop the principles of time-delayed control design for the active control of structures in which the presence of large time delays in the control loop may make it difficult for their effects to be easily eliminated and/or compensated. A control design strategy is proposed that is different from what has been generally accepted hereto; it calls for taking advantage of these large, inherent time delays in the control design. The presence of large time delays in the control loop requires that we understand the infinite dimensionality of the system and so we introduce the concept of non-system poles. This is first done within the framework of an SDOF system with time-delayed velocity feedback control. Several new results are presented dealing with stability and performance issues. These results include and extend those available to date. Having developed control design principles with an SDOF system as the underlying basis, these principles are then developed for multi-actuator, multiple time-delay control of MDOF systems. A numerical example of a building structure modeled as an MDOF system that is subjected to strong earthquake ground shaking is presented. The control design based on the underlying principles shows good stability characteristics and effective performance behavior. We demonstrate its application to a structure subjected to strong earthquake ground shaking, thereby showing its usefulness in hazard mitigation. Copyright © 2005 John Wiley & Sons, Ltd.

Active control of structures using time delayed positive feedback proportional control designs

This paper explores a new methodology for the active control of structures through the use of time delayed, positive feedback proportional control. The idea is to utilize intentional time delays, which may not necessarily be small when compared with the natural periods of vibration of a structure. Such time delayed systems are infinite dimensional. Analytical and computational results related to both system and non-system poles are herein provided for the first time. Results related to the stability of the presented control methodology are given. The efficacy of the control design is illustrated by applying it to a structure modelled as a single-degree-of-freedom system subjected to strong earthquake ground shaking. It is shown that while displaying good stability characteristics, the performance of such time delayed positive feedback proportional control can be even superior—in terms of both, reduced structural response, and reduced control effort—to standard proportional negative feedback control designs with no time delay. Copyright © 2005 John Wiley & Sons, Ltd.

Time delayed control of structural systems

AbstractTime delays are ubiquitous in control systems. They usually enter because of the sensors and actuators used in them. Traditionally, time delays have been thought to have a deleterious effect on both the stability and the performance of controlled systems, and much research has been done in attempting to eliminate them, compensate for them, or nullify their presence. In this paper we take a different view. We investigate whether purposefully injected time delays can be used to improve both the system's stability and performance. Our analytical, numerical, and experimental investigation shows that this can indeed be done. Analytical results of the effects of time delays on collocated and non‐collocated control of classically damped and non‐classically damped systems are given. Experimental and numerical results confirm the theoretical expectations. Issues of system uncertainties and robustness of time delayed control are addressed. The results are of practical value in improving the performance and stability of controllers because these characteristics (performance and stability) improve dramatically with the intentional injection of small time delays in the control system. The introduction of such time delays constitutes a ‘minimal change’ to a controller already installed in a structural system for active control. Hence, from a practical standpoint, time delays can be implemented in a nearly costless and highly reliable manner to improve control performance and stability, an aspect that cannot be ignored when dealing with the economics and safety of large structural systems subjected to strong earthquake ground shaking. Copyright © 2003 John Wiley & Sons, Ltd.

Seismic-reflection imaging of Tertiary faulting and related post-Eocene deformation 20 km north of Memphis, Tennessee

Other than the Crittenden County fault zone (CCFZ), little is known about the seismic hazard from earthquake faults within 50km of Memphis, Tennessee, a city that contains a large inventory of older buildings that are vulnerable to moderate and strong earthquake ground shaking. To address this lack of knowledge about faulting near Memphis, we acquired a 4.5km long Mini-Sosie seismic-reflection profile across the boundary between the loess-covered bluffs and modern Mississippi River flood plain in Meeman-Shelby Forest State Park north of Memphis. We imaged a previously unknown reverse/thrust fault that displaces Paleozoic and Cretaceous rocks and upwarps Tertiary deposits on the floodplain portion of the profile about 25km north of downtown Memphis. The Paleozoic and Cretaceous rocks are vertically faulted about 70 and 40m, respectively, in an up-to-the-west sense of displacement. The fault displacement apparently terminates in the basal portion of the Paleocene section and causes only an upwarping of the overlying deposits. The overlying Paleocene and Eocene deposits, which are probably the youngest deposits imaged, are upwarped about 50–60m with the same sense of displacement as the underlying older units. The sense of displacement, amplitude, and appearance of the fault in the seismic data are very similar to that observed in the seismic reflection images of the CCFZ 15km west of this profile. Although we have imaged this new fault in only one location, its proximity to Memphis and similarities to the CCFZ, leads us to speculate that it may be a parallel structure to the CCFZ and thus warrants further study.

Experiments on Steel MRF Building with Supplemental Tendon System

An experimental and analytical study is presented that investigates the effectiveness of a supple- mental damping system consisting of elastomeric spring dampers (ESD) and fuse-bars to mitigate the seismic response of steel structures. Steel structures generally possess significant flexibility and relatively low inherent viscous damping. Under strong earthquake ground shaking, large interstory drifts can be expected which in turn cause distress to both structural and nonstructural elements. In this study, a load-balancing tendon fuse1damper (TFD) system has been adopted, where sacrificial yielding fuse-bars are used parallel to ESD devices to initially help stiffen the structure. A total of seven different configurations were tested with various bracing as well as supplemental damping systems. It was both experimentally observed and analytically shown that the proposed supplemental tendon system significantly attenuates the overall seismic response of the structure. An improved velocity-dependent computational model for the ESD devices is presented and verified. Hence, benefits of using a load balancing-draped tendon profile are analytically investigated. INTRODUCTION Because steel-moment-frame structures did not perform par- ticularly well in the recent Northridge earthquake, it is nec- essary for the profession to investigate both direct and indirect means of mitigating the effects of inherently faulty welded steel beam-column connections designed prior to 1994. Direct methods of structural improvement principally involve strengthening or structurally modifying elements to enhance the ductility of the welded beam-column connections. Much research sponsored by SAC (a joint venture) has been directed toward this end (SAC 1997). It is the premise of the research presented here that indirect methods of mitigation should also be investigated—as an alternative or supplement to direct strengthening or ductility improvements. Whereas direct meth- ods aim to enhance the ductility capacity of components, in- direct methods embrace supplemental damping and/or bracing, with the intent to minimize the ductility demand on the struc- tural system. Another important consideration in the earthquake-resistant design and retrofit of structures is near-source ground motions and their damage potential, especially on flexible buildings. In one recent study (Hall et al. 1995) it was pointed out that the displacement pulses at or near the natural period of vibration of the structure may cause severe damage to the structure, as excessive interstory drifts are to be expected. If such pulses occur as part of the first major cycle of the response, the max- imum response is generally not a function of the damping in the structure. Furthermore, it can be shown that maximum de- formation is attained at the end of the pulse. Therefore the effect of damping in reducing the maximum response will be minimal, the dissipated energy being considerably less than that of one full cycle of response. This becomes an important issue in the design of structures with energy-dissipation sys- tems that rely merely on the added damping. For pulse-type ground motions, such as those mentioned above, damper-only systems will help to attenuate the response only after the initial

Residual Displacement Response Spectrum

Structures subjected to strong earthquake ground shaking may be left in a displaced condition. The amount of this residual or permanent displacement is determined by structural characteristics, including mass and hysteretic behavior, as well as ground motion. Residual displacement is undesirable because it presents problems during repair and reconstruction after an earthquake. This paper describes analyses of many single-degree-of-freedom bilinear oscillators, with different natural periods, damping ratios, ductility factors, bilinear factors, and input ground motions. These analyses were carried out in order to obtain a method of estimating the likely residual displacements of real single-degree-of-freedom structures. The residual displacement was normalized by the maximum possible residual displacement. Although there was scatter in the normalized residual displacement for different earthquake records, trends in behavior were dominated by the slope of post-yielding branch of bilinear loop. A residual di...

Statistical extension of response spectrum superposition

This paper, is an extension of our work on peak statistics of single degree of freedom system, and summarizes new results which provide for computation of expected and most probable values of the first largest, second largest, third largest etc. peaks of response of linear, viscously damped n- degree of freedom system. Comparisons with exact numerical simulation on a typical structure show good accuracy for short impulsive, intermediate and for long strong earthquake ground shaking.

Duration of strong earthquake shaking

This paper summarizes recent developments in the analysis, interpretation and estimation of the duration of strong earthquake ground shaking in a form suitable for routine applications. It presents two empirical scaling models for estimating the duration in terms of (1) the Modified Mercalli Intensity at the site, and (2) the magnitude and epicentral distance. Both models consider the influence of (a) the frequency of motion, (b) horizontal or vertical component direction, and (c) the depth of sedimentary deposits beneath the site on the duration of shaking. It is shown that the depth of sedimentary deposits beneath and surrounding the site should play a significant role in the empirical estimation of the duration of strong earthquake shaking.

The identification of building structural systems

abstract This paper investigates the response of structural systems to strong earthquake ground shaking by utilizing some concepts of system identification. After setting up a suitable system model, the Weiner technique of nonparametric identification has been introduced and its experimental applicability studied. The sources of error have been looked into and several new results have been presented on accuracy calculations stemming from the various assumptions in the Wiener technique. The method has been applied in studying the response of a 9-story reinforced concrete structure to earthquake excitation as well as ambient vibration testing. The linear contribution to the total roof response during strong ground shaking has been identified, and it is shown that a marked nonlinear behavior is exhibited by the structure during the strong-motion portion of the excitation.

Variations of strong earthquake ground shaking in the Los Angeles area

Abstract Accelerograms recorded at six stations in the metropolitan Los Angeles area during the Borrego Mountain, 1968, the Lytle Creek, 1970, and the San Fernando, 1971, earthquakes in southern California have been studied. In comparing the ground motions recorded during different earthquakes at each of the six stations and in correlations of these motions recorded at different stations during the same earthquake, those aspects of the analysis which emerge from this study and are relevant for seismic zoning have been emphasized. It has been found that the patterns of strong ground shaking in this area depend predominantly on the mechanism and the distance of an earthquake source from a recording station and that the local soil conditions played only a minor role in modifying the ground motion at this particular area. It has been shown that gross spectral characteristics of ground motion recorded at various stations can be approximately related by the seismic moment at the low-frequency end and by the stress drop at the high-frequency end.