Earthquake Hazard Mitigation Research Articles

Optimum Control System for Seismic and Aerodynamic Flutter Response of Cable-Stayed Bridge Using Magnetorheological Dampers

Control of cable-stayed bridge flutter for earthquake and aerodynamic hazard mitigation represents a relatively new area of research. This paper proposes a new optimized smart control system to mitigate the cable-stayed bridge flutter due to seismic and aerodynamic vibration. A Magnetorheological (MR) fluid damper, which belongs to the class of controllable fluid dampers, is proposed for use in a control strategy for mitigating its effect on the cable-stayed bridge. Genetic algorithm is adopted to determine the flutter acceleration levels, and corresponding forces of MR dampers. The optimized forces values from MR dampers are studied under the effect of five strong earthquakes recorded, known as El-Centro, Mexico City, San Fernando, Ker Country, and Northridge earthquakes. The time delay between the monitoring system and the actuator response is also studied. The simulation and optimization results shows that the proposed control strategy using MR dampers is the promising one of the applicable control methods to reduce the seismic and aerodynamic flutter vibration of the stayed bridge.

Sociological and behavioural impediments to earthquake hazard mitigation

PurposeThe purpose of this paper is to examine the behavioural and sociological impediments to successful implementation of earthquake hazard mitigation and to recommend possible intervention strategies.Design/methodology/approachData were gathered through a case study methodology and interviews adopted as the research strategy. A semi‐structured questionnaire was chosen as a data‐collection instrument, with 33 interviews conducted for various stakeholders involved in seismic retrofit decision‐making process.FindingsThe research main findings include the role of risk perception in diminishing earthquake hazard mitigation, difficulties in assessing benefits and values of seismic retrofit implementation and the hazard mitigation approach adopted by governmental organisations. The findings suggested that stakeholders involved in retrofit decision‐making should have a good understanding of the risks faced as well as the implications of their decisions.Originality/valueThe paper investigates earthquake hazard mitigation of commercial buildings at the stakeholders‐level by adopting a multidisciplinary approach that incorporated decision sciences, policy perspectives and socio‐behavioural perspectives. The findings highlight the significance of stakeholders approach to foster adequate mitigation of earthquake risks.

Seismic response analysis of adjacent buildings connected with MR dampers

The mutual impacts between two adjacent tall buildings during past major earthquakes have caused significant damage. Researchers have examined the effectiveness of various seismic control devices for interconnecting two adjacent buildings for earthquake hazard mitigation. In this study, the effectiveness of MR damper is examined for seismic response mitigation of adjacent multistory buildings under coupled building control scheme, involving passive-off, passive-on and semiactive control strategies. Further, the influence of damper location and maximum command voltage, on control performance is also examined. Based on the results of the numerical study it has been observed that the MR damper is an effective device to control the response of both the buildings for a wide range of ground motion.

A Comparative Study of the Least Squares Method and the Genetic Algorithm in Deducing Peak Ground Acceleration Attenuation Relationships

In engineering applications, the development of attenuation relationships in a seismic hazard analysis is a useful way to plan for earthquake hazard mitigation. However, finding an optimal solution is difficult using traditional mathematical methods because of the nonlinearity of many relationships. Furthermore, using unweighted regression analysis in which each recording carries an equal weight is often problematic because of the non-uniform distribution of the data with respect to distance. In this study, the least squares method (LSM) and a genetic algorithm (GA) were employed as optimization methods for an attenuation model to compare the robustness and prediction accuracy of the two methods. Different (equal and unequal) weights of each recording were used to compare the adaptability of the weighting for practical application. The unequal weights of each recording were defined as functions of the hypocentral distance or the shortest distance from a station to the fault on the earth’s surface. Finally, regression analysis of horizontal peak ground acceleration (PGA) attenuation model in southwest Taiwan was shown.

An Experimental Multi-disciplinary observatory (VENUS) at the Ryukyu Trench using the Guam-Okinawa Geophysical Submarine Cable

A MultiDisciplinary Ocean Bottom Observatory (MDOBO) was installed on VENUS (Versatile Eco-monitor- ing Network by Undersea-cable System) at a depth of 2170 m on the slope of the Ryukyu Trench. In this con- text, «Eco-»refers to both economic (e.g., earthquake hazard mitigation) and ecological motivation. The first step in this instillation was to insert a telemetry/power system into the submarine coaxial cable; this system could then service the MDOBO, which consists of seven major bottom sensor packages. During August-Sep- tember 1999, using a deep-towed unit and both manned and unmanned submersibles coupled with precise ship navigation, the MDOBO system and its attendant cables were deployed over a range of distances from 80 m to 1 km from the telemetry system, with several meters allowance for navigational uncertainty in positioning. The unmanned submersible then extended the multi-conductor extension cables from the instrument units toward the telemetry system and connected them to undersea mateable connectors on a junction box installed on the submarine cable. The MDOBO collected one and half months of continuous records. Several kinds of useful data were collected after installation, including an aftershock (Ms= 6.1) of the 1999 Chi-Chi earthquake (Ms= 7.7) in Taiwan.

Seismotektonik dan Potensi Kegempaan Wilayah Jawa

http://dx.doi.org/10.17014/ijog.vol3no4.20085A seismogenetic study shows the Jawa Island Arc and its subduction zone system belong to a highly active seismotectonic arc unit (west Jawa and Sumatera) and an active seismotectonic arc unit (western part of West Jawa – Central Jawa – East Jawa). In general, these regions are part of the Indonesian Earthquake Hazard Zones No. VI, VII, VII and IX. The regions are characterized by the presence of rare earthquake of magnitude > 8.5 Richter Scale (western part of Java), frequent magnitude of 7 Richter Scale and common 5 - 6 Richter Scale (Southern part of Java). The potential hazardous earthquake in Jawa that is > 5,6 Richter Scale of magnitude and shallow depth (< 30 km) is due to a subduction zone earthquake. Epicenter distance, magnitude, geological site conditions, population, and infrastructure are the index of earthquake hazard and risk in these regions. The earthquake hazard mitigation programme in the near future is a risk assesment based on macro and microzonation of earthquake hazard and risk. These macrozonation and microzonation assessments are essentially needed for provinces, districts, and cities.

Toward earthquake early warning in northern California

Earthquake early warning systems are an approach to earthquake hazard mitigation which takes advantage of the rapid availability of earthquake information to quantify the hazard associated with an earthquake and issue a prediction of impending ground motion prior to its arrival in populated or otherwise sensitive areas. One such method, Earthquake Alarm Systems (ElarmS) has been under development in southern California and, more recently, in northern California. Event magnitude is estimated using the peak amplitude and the maximum predominant period of the initial P wave. ElarmS incorporates ground motion prediction equations and algorithms from ShakeMap for prediction of ground motions in advance of the S wave arrival. The first peak ground motion estimates are available 1 s after the first P wave trigger, and are updated each second thereafter for the duration of the event. The ElarmS methodology has been calibrated using 43 events ranging in size from ML 3.0 to Mw 7.1 that occurred in northern California since 2001. We present the results of this calibration, as well as the first implementation of ElarmS in an automated, noninteractive setting and the results of 8 months of noninteractive operation in northern California. Between February and September 2006, ElarmS successfully processed 75 events between Md 2.86 to Mw 5.0. We find that the ElarmS methodology processed these events reliably and accurately in the noninteractive setting. The median warning time afforded by this method is 49 s at the major population centers of the Bay Area. For these events the magnitude estimate is within an average of 0.5 units of the network‐derived magnitude, and the ground motion prediction from ElarmS is within an average of 0.1 units of the observed modified Mercalli intensity.

Application of smart passive damping system using MR damper to highway bridge structure

Magnetorheological (i.e., MR) dampers are one of the most prospective semiactive control devices for civil engineering applications to earthquake hazard mitigation, because they have many advantages such as small power requirement, reliability, and low price to manufacture. A smart passive system based on an MR damper system without including a power supply, controller, and sensors consists of an MR damper and an electromagnetic induction (i.e., EMI) system that uses a permanent magnet and a coil. The electromotive force induced by movement of a structure can control MR damper effectively without any external power supply and control algorithm. This smart passive control system is implemented to verify the effectiveness for seismic protection of benchmark structural control problem for the seismically excited highway bridge, which is based on the newly constructed 91/5 highway over-crossing in Southern California. The results of the numerical simulations show that the presented control system can be beneficial in reducing seismic responses of benchmark bridge structure.

Time-Delayed Positive Velocity Feedback Control Design for Active Control of Structures

In this paper we present and propose a design methodology that uses intentional time delays for the active control of structures. We use here positive velocity-feedback, time-delayed control and show that its performance is, in general, superior to the previously developed methodology of using time delayed, negative velocity-feedback control. A detailed study carried out in this paper of the nonsystem poles and their interaction with the system poles reveals the reasons for this. Analytical results related to performance and stability of the new method are presented. We apply the time delayed positive velocity feedback active control methodology to a multidegree-of-freedom system subjected to the S00E component of ground acceleration recorded during the El Centro 1940 earthquake. The excellent behavior in terms of stability, performance, and control efficiency that is demonstrated by our time-delayed control design as well as its facile implementation makes it attractive for earthquake hazard mitigation in a practical sense.

Residents' attitudes toward a land-use control for earthquake hazard mitigation in Kanazawa city, Japan

Residents' attitudes toward a land-use control for earthquake hazard mitigation in Kanazawa city, Japan

Inversion of the HZ ratio of microseisms forS-wave velocity in the crust

SUMMARY S-wave velocity in the shallow crust is an important controlling parameter for ground motion amplification. It is a key parameter for prediction of ground motion and thus for earthquake hazard mitigation in general. Shallow S-wave velocity structure has often been obtained from phase velocity of microtremors and microseisms. We present a new approach which directly inverts the ratio of horizontal to vertical amplitudes of microseisms which is referred to as the HZ ratio in this paper. Our approach consists of (i) isolation of Rayleigh-wave dominant portions in seismograms by using the 90-degree phase shift between horizontal and vertical component, (ii) measurement of the HZ ratios as a function of frequency and (iii) iterative inversion for S-wave velocity structure in the crust. Depth sensitivity kernels of the HZ ratios for density, P-wave velocity and S-wave velocity are derived by a numerical method. Examples of the application of this method to data in southern California show that the HZ ratio data require modification of the standard seismic velocity model in this region (Southern California Earthquake Center Community Velocity Model 3.0 or SCEC CVM) in the upper 10–15 km. The derived models show amplification of incident SH waves by factors of 2–8, relative to the prediction by the SCEC CVM. The proposed approach has promise for applications to other regions in the world because microseisms are observed everywhere in the world. The method may become even more powerful if it is combined with phase velocity data.

Quantitative analysis of surface coseismic faulting and postseismic creep accompanying the 2003, Mw = 6.5, Chengkung earthquake in eastern Taiwan

On the basis of field observations and geodetic measurements we analyzed coseismic and postseismic deformation of the 2003, Mw = 6.5, Chengkung earthquake across the rupture trace of the Chihshang fault, which lies along the suture zone between the Philippine Sea plate and the Eurasian plate in eastern Taiwan. At three of our investigation sites along the Chihshang fault the earthquake deformation was exhibited by fresh fractures within the 150‐ to 200‐m‐wide surface fault zone, reactivating preexisting fractures in most cases. In addition to daily recorded creep meter data, geodetic measurements, including leveling, distance‐and‐angle electronic distance meters, and GPS measurements, were carried out during surveys 20–25 days before, 20–25 days after, and 120–125 days after the earthquake. The near–fault surface deformation is mainly characterized by anticlinal folding in the hanging wall and minor gentle synclinal folding in the footwall. The geodetic data show that within our 150‐ to 250‐m‐wide networks the coseismic deformation of the main shock produced only about 1–2 cm of horizontal shortening and vertical offset across the fault zone. A larger additional displacement of about 7–9 cm for both the horizontal shortening and the vertical offset occurred as postseismic creep during the 120–125 days following the main shock. We interpret the predominant folding and the rather large postseismic creep as a result of strong velocity strengthening along the fault plane near the surface, which caused locking or coupling effect during the coseismic rupturing. The depth of locked segment, along which the coseismic and postseismic slip decreased dramatically upward, is estimated to be 25–100 m, depending on the site. We interpreted the velocity strengthening and coupling effect at the shallow level as viscoelastic behavior of unconsolidated deposits in the footwall and mélange mudstone in the hanging wall. By incorporating far‐fault continuous GPS data, it was found that minor but significant deformation occurred outside of the surface ruptures zone of the Chihshang fault. In addition, a possible back thrust or back fold might have occurred in the hanging wall. We note that the Chengkung earthquake occurred during the dry season. This is consistent with the fact that the mechanical coupling of the fault at shallow depth is higher during drier periods, inferred from the previous seasonal creep data. At outcrop scale, regarding damage of construction such as a concrete retaining wall, most of the coseismic and postseismic horizontal shortening was essentially absorbed by multiple distributed brittle ruptures, which deserves attention in terms of earthquake hazard mitigation.

Smart passive system based on magnetorheological damper

Magnetorheological (MR) dampers are one of the most promising control devices for civilengineering applications to earthquake hazard mitigation, because they have manyadvantages such as small power requirement, reliability, and low price to manufacture. Toreduce the responses of the controlled structure by using MR dampers, a controlsystem including a power supply, controller, and sensors is needed. However,when a lot of MR dampers are applied to large-scale civil structures, such ascable-stayed bridges and high-rise buildings, the control system becomes complex. Thus,it is not easy to install and to maintain the MR damper-based control system.In this paper, to resolve the above difficulties, a smart passive system is proposed, which isbased on an MR damper system. The smart passive system consists of an MR damper andan electromagnetic induction (EMI) system that uses a permanent magnet and a coil.According to the Faraday law of induction, the EMI system that is attached to the MRdamper produces electric energy. The produced energy is applied to the MR damper tovary the damping characteristics of the damper. Thus, the smart passive systemdoes not require any power at all. Furthermore, the output of electric energy isproportional to input loads such as earthquakes, which means the smart passivesystem has adaptability by itself without any controller or corresponding sensors.Therefore, it is easy to build up and maintain the proposed smart passive system.To verify the effectiveness of the proposed smart passive system, the performance iscompared with that of the normal MR damper-based control system. The numerical resultsshow that the smart passive system has comparable performance to the normal MRdamper-based control system.

"Earthquake-proof Safety in Daily Life Infrastructure" Earthquake Hazard Mitigation and Strong Ground Motion Prediction

"Earthquake-proof Safety in Daily Life Infrastructure" Earthquake Hazard Mitigation and Strong Ground Motion Prediction

Consideration of Earthquake Hazard Mitigation as a Component of Water/Wastewater Facility Modification and Expansion

Consideration of Earthquake Hazard Mitigation as a Component of Water/Wastewater Facility Modification and Expansion

Proposal of a National Mitigation Strategy Against Earthquakes in Turkey

While laboratory and analytical studies can provide valuable information about earthquake hazard mitigation, the most effective educator is the impact of a full-scale earthquake on a full-scale city. The recent earthquakes in Turkey showed that the governmental as well as individual attitudes towards earthquakes did not represent proportionate responses to the risk levels concerned. Turkey had weaknesses in preparing, planning, mitigating and responding to disasters in spite of the known seismic vulnerability of the country. Many steps have been taken after 1999 earthquakes in Turkey, however, the preparations largely concentrate on the response and recovery phases and a fundamental step to reform the current disaster management system and steps to rehabilitate the vulnerable building stock has not been undertaken until today. This would involve changing the present laws and regulations and de-centralising the disaster management system. The aim of this paper is to propose a national mitigation strategy for Turkey for a time-frame of 10 years. The model proposed is a very comprehensive model for earthquake risk reduction in Turkey and within this context, the legislative and technical aspects of mitigation will be discussed in detail. Strategies for mitigating and retrofitting the existing building stock will also be proposed.

Foundation Isolation for Seismic Protection Using a Smooth Synthetic Liner

Smooth synthetic materials placed underneath foundations of structures can provide seismic protection by absorbing energy through sliding. Cyclic and shaking table tests were conducted on a variety of synthetic interfaces to identify a suitable liner for use as foundation isolation. It was concluded that a high strength, nonwoven geotextile placed over an ultrahigh molecular weight polyethylene, UHMWPE (geotextile/UHMWPE) constitutes a liner that is well suited for this application. The static friction coefficient of the interface (between the geotextile and the UHMWPE) is about 0.1. The dynamic coefficient is about 0.07 and is insensitive to changes in slip rate and normal stress. A single-story structural model with and without foundation isolation was tested using a shaker table. The results demonstrate the role of foundation isolation in substantially reducing the seismic shear forces in the model. Accompanying this reduction in shear forces are slip displacements along the isolation liner. Permanent slip (final location of the structure relative to its initial position) can be reduced through the use of a small restoring force that could be provided through passive soil resistance. Peak-to-peak slip (maximum slip during shaking) needs to be permitted for foundation isolation to be effective. The experimental and analytical research results demonstrate the technical feasibility of using a smooth synthetic liner in earthquake hazard mitigation.

新潟県を例とした被害地震に基づく積雪寒冷期地震に対する住民の防災意識調査

Earthquake is one of the main disasters in Japan. But many people seem to be interested only in earthquake hazard mitigation and preparedness on the Great Hanshin-Awaji (Kobe) Earthquake. Although the researches on such mitigation are in progress, there is still lack in research as well as in strategy against the possible hazard due to earthquake during snow periods.Niigata Prefecture also experienced various fault irrespective sized earthquakes during the snow seasons in the past, which did huge devastation. Nagaoka Earthquake (1961), Niigata Ken Nanseibu Earthquake (1992), Niigata Ken Hokubu Earthquake (1995) and Niigata Ken Chubu Earthquake (1999) are typical examples.Present study focuses on the hazard mitigation approach against the earthquake disaster during snow season. The hazard situation is mainly analyzed through the survey results based on the inhabitant's concept on the administered questionnaires.

Possibility of Forecasting Aftershock Distributions from Stress Change: A Case Study of Inland Taiwan Earthquakes

Spatial heterogeneous slip dislocation models from seismic waveform inversions of several moderate to large earthquakes in the past decade in the Taiwan area are used to calculate stress transfer conditions associated with aftershock distributions. Regardless of the possibility of aftershocks along different fault planes to the mainshock, stress change calculations for optimum orientation planes after the mainshock show a great degree of consistency in positive stress change to aftershock distribution. Toward the possibility of forecasting aftershock distributions from stress changes due to the mainshock, we considered homogeneous fault models on the basis of earthquake scaling law to produce rapid stress change calculations. Stress changes from homogeneous and heterogeneous fault models show similar patterns. They both show good correlation with aftershock distributions, even for the complex fault rupture of the 1999 Chi-Chi, Taiwan, earthquake. Our results, thus, support the possibility of forecasting aftershock distributions using mainshock stress changes. Once the location, magnitude and focal mechanism of an earthquake become available, stress change calculations can be carried out to forecast aftershock distribution for earthquake hazard mitigation.

The impact of total acceleration control for semi-active earthquake hazard mitigation

Total structural acceleration regulation is a means of managing structural response energy and enhancing the performance of civil structures undergoing large seismic events. A quadratic output regulator that minimizes the total structural acceleration energy is developed and tested on a realistic non-linear, semi-active structural control case study. Suites of large scaled earthquakes are used to quantify statistically the impact of this type of control in terms of changes in the statistical distribution of controlled structural response. Structural responses are shown and statistically characterised for a three-story steel moment-resisting frame with realistic non-linear behavior. Total structural acceleration control is shown to be more effective than typical displacement focused optimal structural control methods, by providing equivalent or better performance in terms of displacement and hysteretic energy reductions, while also significantly reducing peak story accelerations and the associated damage and occupant injury. For earthquake engineers faced with the dilemma of balancing displacement and acceleration demands this control strategy essentially eliminates that concern, making it a very attractive solution to mitigate seismic hazards. These results are also presented in a unique graphical form showing the statistical distribution to highlight the impact of control for a suite of ground motions with a given probability of occurrence. Hence, by presenting structural response in terms of statistical distribution, rather than specific data, the results, as best seen graphically, are immediately applicable to a variety of standard hazard analysis methods, which lie at the core of the trend towards performance-based design in earthquake engineering.