Strong Ground Motion Recordings Research Articles

The Damage Assessment for Rapid Response (DARR) Method and its Application to Different Ground-Motion Levels and Building Types

AbstractSeismic recordings in buildings and on the ground are increasingly available due to the increment and expansion of seismic monitoring networks worldwide. However, most urban strong-motion networks consist of stations installed at the ground or, less frequently, in selected building’s basement. It is, therefore, of utmost importance to develop methods that can provide estimates of expected structural damage, starting from earthquake recordings at the ground level. Damage Assessment for Rapid Response (DARR) provides first-level estimates of the expected damage to buildings, based on ground-motion recordings and simple information on buildings’ characteristics. In this work, we apply DARR using both weak and strong ground-motion recordings available for different low- and mid-rise building typologies. A total of 9 buildings and 19 earthquake recordings were analyzed. DARR reproduces the shaking at the building’s top, and estimates the peak structural relative displacement or average interstory drift. Results show that the method works well for the considered building types and ground-motion levels for the estimation of relative and total displacements using first-order assessments. Comparison with the previously defined thresholds allows the estimation of expected damage. Our results (i.e., no damage for most buildings and events) are consistent with the absence of damaging events in northeastern Italy in the studied period (2019–2021). For a school building in central Italy, which was heavily damaged by the 2016 Central Italian sequence, DARR correctly predicted this fact.

Joint Autocorrelation and Receiver Function Analysis of Sedimentary Structures Using Strong Ground Motion Records

Joint Autocorrelation and Receiver Function Analysis of Sedimentary Structures Using Strong Ground Motion Records

1D nonlinear site response analysis of the Isparta Basin (Southwestern Turkey) with surface wave (ReMi) and borehole data

This study presents a soil-response analysis of Isparta basin, is situated in the one of most important tectonic areas, using surface wave (ReMi™) and borehole data at 24 points. In the analysis, the nonlinear site response analysis approach was carried out using the DeepSoil software. The study area was characterized by C and D soil class according to NEHRP (National Earthquake Hazards Reduction Program) and TBEC-2018 (Turkish Building Earthquake Code-2018) soil classification criteria. For the modelling, the strong ground motion recordings of 6.9 Mw Irpinia and 6.4 Mw Dinar were used and the largest peak ground acceleration (PGA) and spectral acceleration (SA) maps of the study area were created. The Bdr-1914 model was made using Irpinia record, PGA values in the study area were determined in the range of 0.28–0.41 g and SA in the range of 0.77–1.82 g. In the Dnr-1995 model, the PGA values in the basin were found to be between 0.05–0.1 g and SA was within the range of 0.21–0.48 g. It was observed that the spectral accelerations on the surface, which significantly increased the effects of strong ground motion, particularly for Mw 6.9, near the city center and the Cunur area where new settlement areas were dense. The results indicate that ground specific design is required for construction in these areas, which are above the risk threshold in acceleration design spectra. At the same time, these results show the site response studies have critical importance and may make a significant contribution to the design of safe structures in the alluvial basins.

Hellenic Strong-Motion Database with Uniformly Assigned Source and Site Metadata for the Period 1972–2015

AbstractWe present a Hellenic database of intensity measures from uniformly processed strong ground motion recordings, together with metadata on earthquake source attributes and recording site conditions. The database consists of information from 471 earthquakes between 1973 and 2015 that produced 2993 usable recordings from 333 sites. A key element of this work is a unified presentation of data from two major data providers that operate in Greece (Institute of Engineering Seismology and Earthquake Engineering and the Institute of Geodynamics, National Observatory of Athens) along with a university-operated local urban array (University of Patras). Consistent procedures were applied to develop source parameters that include hypocenter locations, moment magnitudes (directly estimated or derived using a conversion procedure), fault-plane solutions, and finite-fault parameters (generally, for events with M>6.0). The time-averaged shear-wave velocity in the upper 30 m parameter is provided for all 333 recording sites based on geophysical measurements where available (102) and proxy-based estimates otherwise. Most events are in the magnitude range of 3.8–7, occurred at shallow hypocentral depths (<30 km), and provide data for rupture distances generally between 10 and 300 km. The combined ground motion, seismic source, and site database is anticipated to be useful for engineering applications, including ground-motion model development and time series selection for response-history analyses.

Evaluation of Strong Ground Motion Records of September 26, 2019 Offshore Silivri (Marmara Sea) Earthquake

26 Eylül 2019 günü Türkiye yerel saati 13.59’da Silivri açıklarında (Marmara Denizi) Kuzey Anadolu Fay hattı Kumburgaz segmenti üzerinde 6.99 km derinlikte büyüklüğü Mw 5.8 olan deprem meydana gelmiştir. Deprem Tekirdağ ve İstanbul başta olmak üzere Yalova, Kocaeli, Bursa ve Kırklareli illerinde hissedilmiştir. 26 Eylül Silivri depremi, 1999 Kocaeli (Mw 7.6) ve 1999 Düzce (Mw 7.1) depremleri ve artçılarından sonra bölgeyi etkileyen en büyük deprem olması nedeni ile önemlidir. Bu çalışma kapsamında Mw 5.8 Silivri deprem yer hareketi kayıtları incelenmiştir. Yer hareketi parametresi Maksimum Yer İvmesi (PGA), 2014 Yeni Nesil Yer Hareketi Tahmin denklemleri (YHTD - Next Generation Attenuation -NGA- Relations) kullanılarak değerlendirilmiştir. Ayrıca yer hareketi parametreleri (MMI, PGA, Sa 0.2 s, Sa 1.0 s) dağılım haritaları oluşturularak, kaydedilmiş yer hareketleri ile karşılaştırılmıştır. Ayrıca öncü ve artçı depremler değerlendirilerek orta ölçekli Marmara Denizi depremlerinin karakteristiği ortaya konmuştur. Ortaya çıkan enerji miktarı geçmiş büyük ölçekli depremler ile karşılaştırılmıştır.

Performance of low-cost viscoelastic damper for coupling adjacent structures subjected dynamic loads

The application of viscoelastic material to reduce the vibrations of various structures has been interest of many researchers from past three decades. The viscoelastic material as a damper has gained popularity for mitigating the vibrations induced on buildings due to wind or earthquake forces. Despite many viscoelastic damper models are proposed for seismic protection of buildings, still its application is not widely spread in developing countries. Hence, this study focuses on modelling and fabrication of viscoelastic damper using locally available natural rubber. A systematic and detailed analysis on the performance of fabricated damper to reduce the vibrations in buildings is carried out. For this purpose, fifteen story adjacent similar buildings are connected with viscoelastic dampers. The performance of natural rubber based viscoelastic damper to improve the seismic performance of buildings is compared with that of 3 M Viscoelastic damper. Time history analysis of buildings with and without dampers is carried out under strong ground motion record. The top story time history response of displacements values indicates that, these natural rubbers based viscoelastic dampers when coupled with adjacent similar buildings reduces the seismic response significantly.

S-Wave velocity structure exploration of sedimentary layers using seismic interferometry on strong motion records

If seismic interferometry is to be applied to a strong ground motion record, the number of available records is limited, compared with the number of ambient noise records. To begin with, we investigated the characteristics of the autocorrelation function for various strong motion records, and the influence of the component of strong motion records to be used for autocorrelation analysis, in order to maximise the number of records available. We found that the autocorrelation function is not influenced by the event or the component of the strong motion record to be used for the analysis, so that reflected waves can be emphasised when a number of autocorrelation function images are prepared without selecting specific types of record. During autocorrelation analysis, we used spectral whitening that worked to remove frequency-dependent source and path effects. In this way, reflected waves from the seismic bedrock could be observed clearly in the whitened autocorrelation function. In addition, we showed the possibility of using the autocorrelation function for exploration by tuning the S-wave velocity structure model to fit the theoretical Green's function to the stacked autocorrelation function. We also found a relationship between the bandpass filter range in the autocorrelation process and the contribution of the multilayer boundary to the reflected wave, from both theoretical and observational examination. We understand the procedure for selecting an appropriate filter range to observe reflected waves from a desired layer boundary.

Case study on seismic behavior of aseismically designed reinforced concrete frame structures

In this study, the seismic performances of two aseismically designed plan-irregular reinforced concrete frame (RCF) households damaged during the October 23, 2011 Van earthquake are assessed. Since no strong ground motion recordings from the main shock were available, first, strong ground motion parameters of the event are evaluated and then compatible with these parameters suits of real records are selected and scaled to match with the event’s simulated acceleration spectrum to be used in the analytical investigations. The results of previous reconnaissance studies, in which one of the present authors was involved, are then discussed. Capacities of the considered RCF’s are determined applying a 3D single-run adaptive pushover procedure that is capable of considering the effect of plan irregularities. The performance assessment procedure based on the current 2007 Turkish Earthquake Code is then applied to these investigated buildings. Additionally, nonlinear dynamic time history analyses are carried out using the previously selected time histories. The hysteretic behavior of the considered buildings is examined as the consequence of the conducted analyses and considering the different suits of selected ground motions, the seismic response of the buildings is evaluated in terms of interstorey drifts. None of the buildings are found to satisfy the expected performance level. Moreover, the numerical results are found to have good correlation with the field observation results.

Seismic actions on structures in the near-source region of the 2016 central Italy sequence

The central Italy seismic sequence began in the latter half of 2016 and continued well into 2017, causing severe damage in the villages close to the source and causing hundreds of casualties. It is a sequence especially interesting to study, from the perspective of seismic actions experienced by structures, because it saw nine M ≥ 5.0 earthquakes within a period of 5 months, rupturing parts of the complex central Apennine mountain range fault system. Consequently, some of the main earthquake engineering issues that arose are the multiple locations where the code-mandated seismic actions were exceeded in more than one of the main events of the sequence and the number of pre- and low-code existing buildings that suffered heavy damage or collapse due to the intensity of individual earthquakes and the cumulative effect of repeated damaging shocks. The present article picks up on these topics and uses probabilistic seismic hazard, as well as the multitude of strong ground motion recordings available from the sequence, to provide a discussion on certain issues, that are all related to the topical subject of seismic actions. These issues are: (1) the unsurprising exceedance of code spectra in the epicentral areas of strong earthquakes; (2) the particular spectral shape and damaging potential of near-source, pulse-like, ground motions, possibly related to rupture directivity; and (3) structural non-linear behaviour in the wake of a sequence that produces repeated strong shaking without the necessary respite for repair and retrofit operations.

Effect of Shear Wave Velocity of Soil on Behavior of Mid-Rise Reinforced Concrete Frame Structures

The most significant parameter of nonlinear time history analysis is the quality of strong ground motion record which will be used. In this paper, the near-field earthquakes including the forward directivity which have been recorded from two different soil classes were scaled in accordance with the design spectrum of probability of exceedance was 10%. Following this, the nonlinear time history analyses of a typical mid-rise reinforced concrete frame structure were conducted by using the strong ground motion records which were scaled. As a result of the analyses made, the shear force, bending moment and interstory drift ratio curves of structures were acquired for each soil classes. By comparing these curves acquired for different soil classes with each other, the effect of soil characteristics on which the structure will be constructed on the results were discussed. According to this, i t has been observed that as the shear wave velocity of soil decreases, internal forces and displacements in the structure increase

Comparison of Strong Ground Motion Recordings of the Lushan, China, Earthquake of 20 April 2013 with the Next Generation Attenuation (NGA)‐West2 Ground‐Motion Models

Abstract A total of 39 free‐field accelerograms in the 2013 M w 6.7 Lushan earthquake, with the closest site‐to‐rupture distances ( R rup ) being less than 200 km, are compared with the median ground motions predicted by the recent Next Generation Attenuation (NGA)‐West2 ground‐motion prediction equations (GMPEs). Overall, for most Lushan station recordings over the whole range of R rup , the spectral acceleration (SA) of the peak ground acceleration (PGA) and of T =0.06 s are within one standard deviation of the predictions from the five NGA‐West2 GMPEs. Most intraevent residuals also fall between plus and minus one standard deviation from the predictions. Moreover, the standard deviation of intraevent residuals are smaller for SA of T =0.06 s than for PGA, which suggests that the application of NGA‐West2 in predicting high‐frequency ground motion due to the Lushan earthquake is acceptable. The spatial contours of intraevent residuals for PGA predicted by the five NGA‐West2 models are almost the same, all showing four regions of negative intraevent residuals. Three of these regions are mainly distributed with the source‐to‐site azimuth approximating to 90° or −90° and the other one approximating to −180°, which are consistent with the extrusion and rupture directions of the Lushan earthquake fault. In general, the five NGA‐West2 GMPEs generate relatively large intraevent residuals at the long period ( T =1.0 s) for R rup exceeding 100 km, although the intraevent residuals are not as large. The short‐period hanging‐wall effects are more consistent with the NGA‐West2 hanging‐wall scaling than those of long period, and the short‐period ground motions on the footwall are more consistent with the NGA‐West2 models than those on the hanging wall.

Development of fragility curves by incorporating new spectral shape indicators and a weighted damage index: case study of steel braced frames in the city of Mashhad, Iran

In this study, strong ground motion record (SGMR) selection based on Eta (η) as a spectral shape indicator has been investigated as applied to steel braced frame structures. A probabilistic seismic hazard disaggregation analysis for the definition of the target Epsilon (e) and the target Eta (η) values at different hazard levels is presented, taking into account appropriately selected SGMR’s. Fragility curves are developed for different limit states corresponding to three representative models of typical steel braced frames having significant irregularities in plan, by means of a weighted damage index. The results show that spectral shape indicators have an important effect on the predicted median structural capacities, and also that the parameter η is a more robust predictor of damage than searching for records with appropriate e values.

Newmark displacement model for landslides induced by the 2013 Ms 7.0 Lushan earthquake, China

Predicting approximate earthquake-induced landslide displacements is helpful for assessing earthquake hazards and designing slopes to withstand future earthquake shaking. In this work, the basic methodology outlined by Jibson (1993) is applied to derive the Newmark displacement of landslides based on strong ground-motion recordings during the 2013 Lushan Ms 7.0 earthquake. By analyzing the relationships between Arias intensity, Newmark displacement, and critical acceleration of the Lushan earthquake, formulas of the Jibson93 and its modified models are shown to be applicable to the Lushan earthquake dataset. Different empirical equations with new fitting coefficients for estimating Newmark displacement are then developed for comparative analysis. The results indicate that a modified model has a better goodness of fit and a smaller estimation error for the Jibson93 formula. It indicates that the modified model may be more reasonable for the dataset of the Lushan earthquake. The analysis of results also suggests that a global equation is not ideally suited to directly estimate the Newmark displacements of landslides induced by one specific earthquake. Rather it is empirically better to perform a new multivariate regression analysis to derive new coefficients for the global equation using the dataset of the specific earthquake. The results presented in this paper can be applied to a future co-seismic landslide hazard assessment to inform reconstruction efforts in the area affected by the 2013 Lushan Ms 7.0 earthquake, and for future disaster prevention and mitigation.

Spectral Characterization of Himalayan Near-Fault Ground Motion

Near-Fault Ground Motion (NFGM) spectral characteristics of three moderate-sized Himalayan earthquakes, viz., the 1986 Dharamsala earthquake (Mw = 5:5), the 1991 Uttarkashi earthquake (Mw = 6:8), and the 1999 Chamoli earthquake (Mw = 6:5) have been studied from the 33 available strong ground motion recordings. Pulse characteristics of fault-normal components in terms of pulse-periods and pulse-indicators have been extracted adopting wavelet analysis. Seven mother wavelets were used in the analysis, and it was found that db4 and db7 mother wavelets were more efficient in extracting the pulse-type characteristics. NFGM spectra, at Bhatwari and Gopeshwar stations, showed higher spectral amplitudes in the velocity-sensitive and acceleration-sensitive regions compared to Indian codal response spectra. This is attributed to high PGV/PGA ratios. The study shows that NFGM leads to widening of acceleration-sensitive region, and the structures that are designed according to the Indian seismic code as flexible structures shall behave as stiff structures when subjected to NFGM.

Nonlinear site response from the strong ground-motion recordings in western China

Strong ground-motion records from the mainshocks and aftershocks of the 2008 Wenchuan (Ms 8.0) and 2013 Lushan (Ms 7.0) earthquakes, within 300km from the faults, were used for horizontal-to-vertical spectral ratio (HVSR) analysis. The HVRSs of the S-wave show that the predominant site frequency decreases with increasing ground-motion level, a characteristic of nonlinear dynamic soil response. We applied diffuse field theory and Monte Carlo search in the model space to produce an inverted shear-wave velocity profile using the HVSRs of weak S-wave motions. The inverted velocity structures are significantly different from the initial ones derived from in-situ measurements. We also applied 1-D equivalent-linear site-response analysis to derive the spectral ratios (i.e., transfer function) for the original and inverted soil models, and compared the results with the observed HVRSs of the S-wave motions. The comparisons showed that the spectral ratios from 1-D simulation for the inverted soil models agree quite well with the observed HVRSs. In other words, this study suggests that the HVSR from observed earthquake ground motion resembles the empirical transfer function of nonlinear site-response.

Investigation on site conditions for seismic stations in Romania using H/V spectral ratio

This research evaluates the soil conditions for seismic stations situated in Romania using the horizontal-to-vertical spectral ratio (HVSR). The strong ground motion database assembled for this study consists of 179 analogue and digital strong ground motion recordings from four intermediate-depth Vrancea seismic events with . In the first step of the analysis, the influence of the earthquake magnitude and source-to-site distance on the H/V curves is evaluated. Significant influences from both the earthquake magnitude and hypocentral distance are found especially for soil class A sites. Next, a site classification method proposed in the literature is applied for each seismic station and the soil classes are compared with those obtained from borehole data and from the topographic slope method. In addition, the success and error rates of this method are computed and compared with other studies from the literature. A more in-depth analysis of the H/V results is performed using data from seismic stations in Bucharest and a comparison of the free-field and borehole H/V curves is done for three seismic stations. The results show large differences between the free-field and the borehole curves. As a conclusion, the results from this study represent an intermediary step in the evaluation of the soil conditions for seismic stations in Romania and the need to perform more detailed soil classification analysis is highly emphasized.

Memory‐Efficient Simulation of Frequency‐DependentQ

Memory‐variable methods have been widely applied to approximate frequency‐independent quality factor Q in numerical simulation of wave propagation. The frequency‐independent model is often appropriate for frequencies up to about 1 Hz but at higher frequencies is inconsistent with some regional studies of seismic attenuation. We apply the memory‐variable approach to frequency‐dependent Q models that are constant below, and follow a power‐law above, a chosen transition frequency. We present numerical results for the corresponding memory‐variable relaxation times and weights, obtained by nonnegative least‐squares fitting of the Q ( f ) function, for a range of exponent values; these times and weights can be scaled to an arbitrary transition frequency and a power‐law prefactor, respectively. The resulting memory‐variable formulation can be used with numerical wave‐propagation solvers based on methods such as finite differences (FDs) or spectral elements and may be implemented in either conventional or coarse‐grained form. In the coarse‐grained approach, we fit effective Q for low‐ Q values (<200) using a nonlinear inversion technique and use an interpolation formula to find the corresponding weighting coefficients for arbitrary Q . A 3D staggered‐grid FD implementation closely approximates the frequency–wavenumber solution to both a half‐space and a layered model with a shallow dislocation source for Q as low as 20 over a bandwidth of two decades. We compare the effects of different power‐law exponents using a finite‐fault source model of the 2008 M w 5.4 Chino Hills, California, earthquake and find that Q ( f ) models generally better fit the strong‐motion data than the constant Q models for frequencies above 1 Hz. Online Material: Figures comparing finite difference and frequency–wavenumber seismograms for an elastic layered‐model point source simulation. Median spectral acceleration centered at 1 s and Fourier amplitude centered at 0.25 and 2.25 Hz for strong ground motion recordings and synthetics from the Chino Hills earthquake.

Investigation of the soil amplification factor in the Adapazari region

Turkey is located on the highly active Eurasian plate. A very active strike slip fault, the North Anatolian Fault Zone (NAFZ), crosses Turkey from east to west; earthquakes occurred on this fault on August 17, 1999 (Kocaeli) and November 12, 1999 (Duzce). Regional geology and subsoil conditions can significantly change the characteristics of ground motion. For this reason, determining soil amplification during an earthquake, especially for soft soils, is a very important topic for researchers. In this study, one dimensional ground response analyses were performed for selected Adapazari sites using the August 17, 1999 Kocaeli earthquake strong ground motion record with SHAKE2000 software. Soil characteristics and depth to engineering bedrock at the selected sites are different and the observed level of structural damage at these sites during the Kocaeli earthquake was also different. Calculated soil surface response spectrums at these sites were compared with the recommended design spectra of the Turkish Earthquake Code and the Eurocode 8. According to one dimensional ground response analyses, the calculated response spectra of the selected sites exceed the recommended design spectra of the Turkish Earthquake Code and the Eurocode 8. Calculations show that higher amplification ratios occur at higher periods due to soil behaviour. Results of this study indicate that local geological conditions may amplify ground motion at some periods and, due to this amplification, the calculated response spectra may exceed the recommended design spectra. Therefore, it is clear that local site conditions must be considered for earthquake-resistant engineering designs on soft alluvial soil deposits.

Prediction of peak ground acceleration of Iran's tectonic regions using a hybrid soft computing technique

A new model is derived to predict the peak ground acceleration (PGA) utilizing a hybrid method coupling artificial neural network (ANN) and simulated annealing (SA), called SA-ANN. The proposed model relates PGA to earthquake source to site distance, earthquake magnitude, average shear-wave velocity, faulting mechanisms, and focal depth. A database of strong ground-motion recordings of 36 earthquakes, which happened in Iran's tectonic regions, is used to establish the model. For more validity verification, the SA-ANN model is employed to predict the PGA of a part of the database beyond the training data domain. The proposed SA-ANN model is compared with the simple ANN in addition to 10 well-known models proposed in the literature. The proposed model performance is superior to the single ANN and other existing attenuation models. The SA-ANN model is highly correlated to the actual records (R = 0.835 and ρ = 0.0908) and it is subsequently converted into a tractable design equation.

Directivity Detection and Source Properties of the 11 May 2011 Mw 5.2 Lorca, Spain, Earthquake

A kinematic finite‐source study of the 11 May 2011 M w 5.2 Lorca, Spain, earthquake has been performed using broadband data from the Spanish National Network. The nodal plane ambiguity of the double‐couple solution was resolved from finite‐source analysis, and a rupture velocity of 1.8 km s−1 and the northeast–southwest‐striking northwest‐dipping plane was found to best fit the data. This fault plane corresponds to the central sector of the Alhama de Murcia fault (AMF). The resulting slip distribution has a maximum of 19.3 cm and a total seismic moment of 6.25×1016 N·m. A Jackknife test has been performed to estimate the fault plane errors and their consequences in the slip distribution. Also synthetic tests have been performed to evaluate the errors in the finite‐source modeling. From this model, a prediction of the strong ground motion near the fault, corrected for soil amplification, is given in terms of peak ground velocity (PGV), which fits with the observed value at the accelerograph in the city of Lorca. We also compared the PGV converted to modified Mercalli intensity at the surface with the intensity distribution, also showing good agreement. Finally we extracted the directivity pulse from the strong ground motion record at Lorca with 0.5 s period in the transverse component to the AMF direction and 33 cm s−1 PGV. To further analyze the directivity effect, we estimate the duration and azimuthal amplitude distribution of the source time functions, finding them to be shorter and of greater amplitude in the direction of rupture and longer and smaller in amplitude in the opposite direction.