Damage Potential Of Earthquake Research Articles

The role of pore fluids in supershear earthquake ruptures

The intensity and damage potential of earthquakes are linked to the speed at which rupture propagates along sliding crustal faults. Most earthquakes are sub-Rayleigh, with ruptures that are slower than the surface Rayleigh waves. In supershear earthquakes, ruptures are faster than the shear waves, leading to sharp pressure concentrations and larger intensities compared with the more common sub-Rayleigh ones. Despite significant theoretical and experimental advances over the past two decades, the geological and geomechanical controls on rupture speed transitions remain poorly understood. Here we propose that pore fluids play an important role in explaining earthquake rupture speed: the pore pressure may increase sharply at the compressional front during rupture propagation, promoting shear failure ahead of the rupture front and accelerating its propagation into the supershear range. We characterize the transition from sub-Rayleigh to supershear rupture in fluid-saturated rock, and show that the proposed poroelastic weakening mechanism may be a controlling factor for intersonic earthquake ruptures.

Vector-Valued Intensity Measures Based on Spectral Shape to Predict Seismic Fragility Surfaces in Reinforced Concrete Buildings

Although some studies have been conducted to compute fragility surfaces of buildings using vector-valued seismic intensity measures (IMs), in all the cases, the first component of the vector usually is the spectral acceleration at first mode of vibration of the structure Sa(T1). In this study, fragility surfaces of three reinforced concrete buildings (RCB) subjected to narrow-band ground motions obtained from soft soil of Mexico City are computed considering vector-valued IMs based not only on Sa(T1), but also the velocity V(T1), pseudo-velocity Sv(T1), and normalized input energy by the mass EI/m(T1) as the first component. As second component of the vector-valued IMs, the Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV), effective duration (tD), earthquake damage potential (ID) and four Np spectral shape-based parameters obtained through spectral acceleration (NpSa), velocity (NpV), pseudo-velocity (NpSv), and input energy (NpEI) have been analyzed. In order to obtain fragility surfaces, Multinomial Logistic Regression (MLR) was applied. It is observed that those vector-valued IMs based on the spectral shape proxies were more efficient to predict the probability of failure of RCB. For this reason, it is important to consider spectral shape vector-valued IMs in order to reduce uncertainty in the structural response of buildings under earthquakes. Thus, the use of two parameters instead of a single intensity measure improves the efficiency. Moreover, the fragility surfaces can be used for the seismic risk evaluation of buildings.

Influence of Different Parameters on Shear Wave Velocity

Subsurface conditions play a major role in the damage potential of earthquakes. Local geological conditions generate significant amplification of the ground motion. The simple way to characterize the site condition is by estimating the shear wave velocity. The main objective of this paper is to evaluate the influence of silt content, density and confining pressure in the shear wave velocity. Soil samples were collected from different locations of College of Engineering, Guindy campus for conducting the bender element (BE) test. The shear wave velocity(Vs) determined from bender element test for the respective field density were compared with shear wave velocity obtained from Multichannel Analysis of Surface Wave (MASW) test. For understanding the influence of above mentioned parameters the bender element tests were carried out. The important conclusions arrived through the studies are increase in density and confining pressure increases the shear wave velocity but increase in silt content decreases the shear wave velocity. The maximum variation in the shear wave velocity determined from laboratory and field are in the range of 11.62% to 18.5%.

ANALISIS PERCEPATAN GETARAN TANAH MAKSIMUM UNTUK MEMETAKAN RESIKO BENCANA GEMPA BUMI DI KAB PEMALANG, JAWA TENGAH

Peak ground acceleration value can be used to determine the risk level of earthquake damage potential. This research calculated peak ground acceleration (PGA) value of Pemalang which located in central of Java island that nearby Indian-Australian and Europan-Asian tectonic plates subduction. This research has been using earthquake data since 1980 – April 2018 and calculating PGA using Fukushima-Tanaka Equation to map the risk level of earthquake damage potential as a pre-eleminary step of earthquake mitigation. The result of this research showed that Pemalang area has PGA value about 13,89-34,44 gal where the maximum value located in the west part of Pemalang. Based of PGA value classification, Pemalang area has low-risk level of earthquake damage potential.Key words: Peak ground acceleration, Fukushima-Tanaka, earthquake, Pemalang

An Approach to Develop Compound Intensity Measures for Prediction of Damage Potential of Earthquake Records Using Canonical Correlation Analysis

ABSTRACT A ground motion intensity measure (IM) well correlated with structural demand plays an important role in predicting the damage potential of earthquake records. This study presents a new approach to develop a compound IM through canonical correlation analysis (CCA). This method utilizes the ability of CCA to search for two linear combinations to maximize the correlation between the corresponding random vectors. To illustrate, the nonlinear responses of single-degree-of-freedom (SDOF) systems due to 98 real ground motion records are used. In a log-log scale, a compound IM in terms of a linear combination of six non-structure-specific IMs is developed with a maximum dependence on the linearly combined structural demand of both peak displacement and dissipated energy. Through a comprehensive discussion, the feasibility and performance of the presented approach is investigated for SDOF systems over the entire period range. It is found that the developed compound IM shows significantly high-level correlation with structural demand, and the corresponding correlation coefficients are greater than 0.95 at most periods. This validates the effectiveness of the presented method in improving prediction accuracy for earthquake damage potential through considering multiple IMs.

Simple Damage Potential of Earthquake with Low Frequency Content Based on Global Reinforced Concrete (RC) Inelastic Response

A numerical investigation was conducted on the damage potential of 25-low frequency content ground motions (earthquake) normalized to be the maximum of 0.30 g. The damage potential is measured based on several parameters started from the simplest parameter (Level-1) to the complex parameter (Level-5). The global inelastic response of 10-story RC structure subjected to the corresponding ground motions, i.e the base shear, roof horizontal displacement, hysteretic energy and element damage index, have been used as damage indicators. Then, the ground motion parameters were correlated with the damage indicators. Results of the investigation showed that among the damage indicators are well correlated. The A/V ratio is relatively simple parameter (Level-2) and possesses relatively consistent and high correlation coefficient R with the damage indicators. Accordingly, A/V ratio can be stated as simple damage potential to cause severity of the structure under earthquake excitation.

Earthquake damage potential and critical scour depth of bridges exposed to flood and seismic hazards under lateral seismic loads

Many bridges located in seismic hazard regions suffer from serious foundation exposure caused by riverbed scour. Loss of surrounding soil significantly reduces the lateral strength of pile foundations. When the scour depth exceeds a critical level, the strength of the foundation is insufficient to withstand the imposed seismic demand, which induces the potential for unacceptable damage to the piles during an earthquake. This paper presents an analytical approach to assess the earthquake damage potential of bridges with foundation exposure and identify the critical scour depth that causes the seismic performance of a bridge to differ from the original design. The approach employs the well-accepted response spectrum analysis method to determine the maximum seismic response of a bridge. The damage potential of a bridge is assessed by comparing the imposed seismic demand with the strengths of the column and the foundation. The versatility of the analytical approach is illustrated with a numerical example and verified by the nonlinear finite element analysis. The analytical approach is also demonstrated to successfully determine the critical scour depth. Results highlight that relatively shallow scour depths can cause foundation damage during an earthquake, even for bridges designed to provide satisfactory seismic performance.

Comparing vector-valued intensity measures for fragility analysis of steel frames in the case of narrow-band ground motions

Seismic fragility of steel frames subjected to narrow-band motions from soft-soils of Mexico City (Mexico) is evaluated by means of a set of vector-valued ground motion intensity measures (IMs) comprised of two parameters. All the vectors considered have, as the first component, spectral acceleration at the first mode of the structure. As the second component, compared IMs are chosen among peak and integral parameters, the former represent the spectral shape in a range of periods, while the latter refer to cumulative damage potential of earthquakes. The maximum inter-story drift and an energy-based damage index for steel frames are employed as engineering demand parameters for structural performance assessment. As a result of the comparison, it is observed that spectral-shape-based vector-valued IMs have the best explicative power with respect to seismic fragility estimation. Analyses, even if limited to the peculiar ground motions considered, suggest that a recently proposed parameter (Np) is especially promising as a candidate for the next generation of IMs when combined with spectral acceleration. This appears independent of the type of seismic response measure considered.

Regional Arias Intensity Attenuation Relationship for Taiwan Considering VS30

The Arias intensity is a measure of earthquake intensity arrived at through the integration of a square of the acceleration time history. It has been demonstrated to be an effective predictor of earthquake damage potential in relation to short-period structures, liquefaction, and seismic slope stability, and has begun to be considered as a ground-motion measure suitable for use in probabilistic seismic hazard analysis (PSHA), as well as earthquake loss estimation. A new empirical Arias intensity attenuation relationship for shallow crustal earthquakes is developed where both fault type and a continuous site variable VS30 are considered. The relationship is based on a large number of strong-motion records (6570) from a wide range of earth- quake magnitudes (3.9-7.6) from the Taiwan Strong Motion Instrument Program (TSMIP) network. Its functional form is modified from that of Travasarou et al. (2003), which is derived from a point-source model, and the coefficients are determined through nonlinear regression analyses using a mixed-effects model. The results show that the incorporation of VS30 can significantly reduce regression error. The Arias intensity value predicted in the present study is generally similar to that obtained by Travasarou et al. (2003), but is different in detail, being more suitable for usage in PSHA for a tectonically young orogenic belt like that in Taiwan or New Zealand.

Real time monitoring of moment magnitude by waveform inversion

An instantaneous measure of the moment magnitude (Mw) of an ongoing earthquake is estimated from the moment rate function (MRF) determined in real‐time from available seismic data using waveform inversion. Integration of the MRF gives the moment function from which an instantaneousMw is derived. By repeating the inversion procedure at regular intervals while seismic data are coming in we can monitor the evolution of seismic moment and Mw with time. The final size and duration of a strong earthquake can be obtained within 12 to 15 minutes after the origin time. We show examples of Mw monitoring for three large earthquakes at regional distances. The estimated Mw is only weakly sensitive to changes in the assumed source parameters. Depending on the availability of seismic stations close to the epicenter, a rapid estimation of the Mw as a prerequisite for the assessment of earthquake damage potential appears to be feasible.

Detailed gravity survey to help seismic microzonation: Mapping the thickness of unconsolidated deposits in Ottawa, Canada

Abstract In this study, measurements of gravity were made to map and model the thickness of Quaternary deposits (sand and clay) overlying Ordovician limestones in a suburb of Ottawa (Orleans, Ontario). Because ground motion amplification is partly related to the thickness of unconsolidated deposits, this work helps refine the assessment of the earthquake damage potential of the area. It also helps the mapping of clay basins, which can locally exceed 100 m in thickness, where ground motion amplification can occur. Previous work, including well log data and seismic methods, have yielded a wealth of information on near-surface geology in Orleans, thereby providing the necessary constraints to test the applicability of gravity modeling in other locations where other methods cannot always be used. Some 104 gravity stations were occupied in an 8 × 12 km test area in the Orleans. Stations were accurately located with differential GPS that provided centimetric accuracy in elevation. Densities of the unconsolidated Quaternary deposits (Champlain Sea clay) determined on core samples and densities determined on limestone samples from outcrops were used to constrain models of the clay layer overlying the higher density bedrock formations (limestone). The gravity anomaly map delineates areas where clay basins attain > 100 m depth. Assuming a realistic density for the Champlain Sea clays (1.9–2.1 g/cm3), the thickness over the higher density bedrock formations (Ordovician carbonate rocks) was modeled and compared with well logs and two seismic reflection profiles. The models match quite well with the information determined from well logs and seismic methods. It was found that gravity and the thickness of unconsolidated deposits are correlated but the uncertainties in both data sets preclude the definition of a direct correlation between the two. We propose that gravity measurements at a local scale be used as an inexpensive means of mapping the thickness of unconsolidated deposits in low-density urban areas. To obtain meaningful results, three conditions must exist. Firstly, elevations of gravity stations must be measured accurately using differential GPS; secondly, that the regional gravity field must be well defined, and thirdly, that the local geology be simple enough to be realistically represented with a two-layer model.

Seismic site classification and site period mapping of Chennai City using geophysical and geotechnical data

Subsurface conditions play a major role in the damage potential of earthquakes and the seismic soil amplification of a site which is a critical factor affecting the level of ground shaking. Shear wave velocity (Vs) of the soil layer is an important parameter influencing the amplification behaviour of the site. Site characterization in calculating seismic hazards is usually based on the near-surface shear wave velocity values. The average shear wave velocity of the top 30 m of the soil, referred to as (Vs)30 is commonly adopted by competent building codes to classify the sites for earthquake resistant design of structures and in general it is widely used in microzonation studies.

Suitability of rapid energy magnitude determinations for emergency response purposes

SUMMARY It is common practice in the seismological community to use, especially for large earthquakes, the moment magnitude Mw as a unique magnitude parameter to evaluate the earthquake's damage potential. However, as a static measure of earthquake size, Mw does not provide direct information about the released seismic wave energy and its high frequency content, which is the more interesting information both for engineering purposes and for a rapid assessment of the earthquake's shaking potential. Therefore, we recommend to provide to disaster management organizations besides Mw also sufficiently accurate energy magnitude determinations as soon as possible after large earthquakes. We developed and extensively tested a rapid method for calculating the energy magnitude Me within about 10–15 min after an earthquake's occurrence. The method is based on pre-calculated spectral amplitude decay functions obtained from numerical simulations of Green's functions. After empirical validation, the procedure has been applied offline to a large data set of 767 shallow earthquakes that have been grouped according to their type of mechanism (strike-slip, normal faulting, thrust faulting, etc.). The suitability of the proposed approach is discussed by comparing our rapid Me estimates with Mw published by GCMT as well as with Mw and Me reported by the USGS. Mw is on average slightly larger than our Me for all types of mechanisms. No clear dependence on source mechanism is observed for our Me estimates. In contrast, Me from the USGS is generally larger than Mw for strike-slip earthquakes and generally smaller for the other source types. For ∼67 per cent of the event data set our Me differs ≤±0.3 magnitude units (m.u.) from the respective Me values published by the USGS. However, larger discrepancies (up to 0.8 m.u.) may occur for strike-slip events. A reason of that may be the overcorrection of the energy flux applied by the USGS for this type of earthquakes. We follow the original definition of magnitude scales, which does not apply a priori mechanism corrections to measured amplitudes, also since reliable fault-plane solutions are hardly available within 10–15 min after the earthquake origin time. Notable is that our uncorrected Me data show a better linear correlation and less scatter with respect to Mw than Me of the USGS. Finally, by analysing the recordings of representative recent pairs of strong and great earthquakes, we emphasize the importance of combining Mw and Me in the rapid characterization of the seismic source. They are related to different aspects of the source and may differ occasionally even more than 1 m.u. This highlights the usefulness and importance of providing these two magnitude estimates together for a better assessment of an earthquake's shaking potential and/or tsunamigenic potential.

Simplified Method to Include Cumulative Damage in the Seismic Response of Single-Degree-of-Freedom Systems

In this paper a consistent method including damage criteria in the seismic response of single-degree-of-freedom systems is proposed. The method allows the determination of suitably modified strength or displacement inelastic spectra through the introduction of an equivalent damage factor pdam that accounts for earthquake damage potential; analogously capacity spectra could be obtained. Three types of damage indices are considered (Park and Ang index DP&A , energy index DE , and low-cycle fatigue index DF ) and derivation of pdam is pursued for all these cases. Moreover approximate simplified expressions in the function of Cosenza and Manfredi seismological ID index, which accounts for cyclic damage potential of an earthquake, are also proposed. In this way damage capacity spectra are obtained to improve the seismic assessment of existing structures including damage effect.

A study on feasibility of SI for identification of earthquake damages in Taiwan

Using the actual damage data of the strong earthquakes in Taiwan, the effectiveness of the earthquake risk indices, namely, peak ground acceleration (PGA) and spectral intensity (SI), is verified. PGA and Housner's [Housner GW. Spectrum intensity of strong-motion earthquakes. In: Proceedings of symposium on earthquakes and blast effects on structures. EERI, UCLA; 1952] definition of SI are directly compared. A three-parameter spectral intensity system with spectral intensities SI a, SI v, and SI d in the acceleration, velocity, and displacement regions, respectively, is discussed. Here, the effectiveness of SI, SI a, SI v, and SI d has been compared by using the available earthquake-damage data in Taiwan. Three period ranges, namely, 0.1–0.6, 0.6–1.6, and 1.6–3.0 s were used for structures of 1–6 stories, 7–20 stories, and 21 and more stories, respectively. The results indicate that the three-parameter system is a good risk index of the damage potential of earthquakes.

Soil Improvement for Mitigation of Damage During the 1999 Kocaeli Earthquake

Ground modification has been used extensively to reduce earthquake damage at poor soil sites. Case history data are crucial for assessing the effectiveness of such mitigation. Following the 1999 Kocaeli Earthquake (Mw = 7.4), the authors investigated the performance of industrial/commercial facilities along Izmit Bay. The region is vital to Turkey's economy, generating about 10% of the nation's GDP. Soil conditions along the Bay consist of soft, weak soils that increase earthquake damage potential. Soil improvement is being increasingly used in the region as a cost-effective mitigation solution. Our study of four major facilities on improved ground showed the treatment to be effective in mitigating losses relative to facilities on unimproved ground.

Rapid Assessment of Damage Potential of Earthquakes in Taiwan from the Beginning of P Waves

To rapidly assess the potential for damage of an earthquake for purposes of earthquake early warning in Taiwan, we used the peak displacement and velocity amplitudes of the first 3 sec of the P wave. The vertical-component records, high-pass filtered at 0.075 Hz, are used. We found that the peak initial-displacement amplitude (Pd) correlates well with the peak ground-motion displacement (PGD) and the peak ground-motion velocity (PGV) at the same site. When Pd > 0.5 cm, the event is most likely damaging. If Pd is combined with the period parameter τ_c, determined in an earlier study, then τ_c × Pd provides an even more robust parameter for assessing the potential for damage.

Some considerations on the physical measure of seismic intensity

The study on seismic intensity can be traced prior to the time that modern seismology was established. In its early stage the seismic intensity was designed to serve as a measure in scaling the severity of earthquake damage to civil engineering and environmental structures. Also the seismic intensity is usually assigned by engineers and seismologists with one or two characteristic parameters of earthquake ground motions to reflect earthquake damage potential so as to be able to serve as an input earthquake load for seismic design of structures. So choosing a proper parameter to reflect the action of seismic intensity is the main objective of the research on physical measure of seismic intensity. However, since various kinds of structures have quite different damage mechanisms there will exist great differences in damages to different structures located at the same area during the same earthquake. Particularly, In some cases, quite different damages have happened even to the structures of same kind due to many other factors such as different construction materials, different configurations or on the different types of sites where structures located. In addition, the ground motion parameters, which result in damage to structures, are not the single peak value of ground motion. Hence, this paper emphasizes that the research on new physical measure of seismic intensity should not only consider the structural characteristics but also take into account other parameters such as duration, energy of ground motion and so on. In particular, as the physical measures of intensity, different ground motion parameter should be adopted for different structures.

Estimation of Earthquake Damage Potential in Metropolitan Area using DMSP Night-time Imagery and Application for Disaster Damage Assessment

Estimation of Earthquake Damage Potential in Metropolitan Area using DMSP Night-time Imagery and Application for Disaster Damage Assessment

One minute after: Strong-motion map, effective epicenter, and effective magnitude

Abstract This article reports the recent progress on real-time seismic monitoring in Taiwan, particularly the real-time strong-motion monitoring by the Taiwan Central Weather Bureau's telemetered seismic network (CWBSN), which is presently aiming at rapid reporting immediately after a large earthquake occurrence. If rapid reporting can be achieved before the arrival of the strong shaking, earthquake early warning will become possible. CWBSN has achieved the generation of the intensity map, epicenter, and magnitude within 1 min of the occurrence of a large earthquake. Both rapid reporting and early warning are principally applied to large (M ≫ 5) events; the requirement of on-scale waveform recording prompted CWBSN in 1995 to integrate strong-motion sensors (e.g., force-balance accelerometers) into its telemetered seismic monitoring system. Time-domain recursive processing is applied to the multi-channel incoming seismic signals by a group of networked personal computers to generate the intensity map. From the isoseismal contours, an effective epicenter is immediately identified that resides in the middle of the largest (usually the 100-gal) contour curve of the intensity map. An effective magnitude is also defined that can be derived immediately from the surface area covered by the largest (usually the 100-gal) contour curve. For a large event with a finite rupture surface, the epicenter and magnitude so derived are more adequate estimates of the source location and of the strength of destruction. The effective epicenter gives the center of the damage area; it stands in contrast with the conventional epicenter location, which only gives the initial point of rupture nucleation. The effective magnitude reflects more closely the earthquake damage potential, instead of the classical magnitude definition that emphasizes the total energy release. The CWBSN has achieved in obtaining the above crucial source information well within 1 min. This time can further be reduced to better than 30 sec, as illustrated by the example in this article, showing that earthquake early warning is indeed an achievable goal. The rapid reporting and early warning information is electronically transmitted to users to allow rapid response actions, with or without further human intervention.