Performance of buildings with masonry infill walls during the 2011 Lorca earthquake

On Wednesday 11th May 2011 at 6:47 pm (local time) a magnitude 5.1 Mw earthquake occurred 6 km northeast of Lorca with a depth of around 5 km. As a consequence of the shallow depth and the small epicentral distance, important damage was produced in several masonry constructions and even led to the collapse of one of them. Pieces of the facades of several buildings fell down onto the sidewalk, being one of the reasons for the killing of a total of 9 people. The objective of this paper is to describe and analyze the failure patterns observed in reinforced concrete frame buildings with masonry infill walls ranging from 3 to 8 floors in height. Structural as well as non-structural masonry walls suffered important damage that led to redistributions of forces causing in some cases the failure of columns. The importance of the interaction between the structural frames and the infill panels is analyzed by means of non-linear Finite Element Models. The resulting load levels are compared with the member capacities and the changes of the mechanical properties during the seismic event are described and discussed. In the light of the results obtained the observed failure patterns are explained. Some comments are stated concerning the adequacy of the numerical models that are usually used during the design phase for the seismic analysis.     

Anomalous increase in the foF2 critical frequency prior to the Spanish earthquake of May 11, 2011

A study of variations in the critical frequency of the F2 layer (foF2) prior to a shallow-focus eartquake with a magnitude M = 5.1 which occurred in Spain on May 11, 2011, is carried out. The obtained results show that a positive disturbance in the foF2 value was observed at the ionospheric Del’ebre station, which is the closest to the earthquake epicenter. At the same time, no disturbances in foF2 are revealed at ionospheric stations located at a greater distance from the epicenter. This fact makes it possible to conclude that the positive disturbance in the F2 layer observed at the Del’ebre station could have a sesmogenic nature.     

Reassessment of intensity estimates from vulnerability and damage distributions: the 2011 Lorca earthquake

This paper presents a reassessment of the seismic intensity estimated for the 2011 Lorca (southeastern Spain) earthquake based on detailed vulnerability data and its comparison with the observed damage. Building and urban data are gathered in selected areas during a field campaign and are completed with office work. The significance of vulnerability modifiers in the final vulnerability distribution is analyzed, and their relation with observed damage trends is explored. A direct application of the vulnerability modifiers is not capable of reproducing the observed damage patterns. A significant increase of vulnerability related to the performance of buildings presenting soft story is required to reach a damage distribution consistent with intensity estimates in the study areas. Accordingly, an intensity increase in certain study zones (as compared to other areas of the city of Lorca) is suggested. Although the approach followed in this study is applied in a city of Spain, it can be extrapolated to other areas where detailed vulnerability assessment is feasible and damage data are available.     

The structural role played by masonry infills on RC building performances after the 2011 Lorca,Spain, earthquake

On May 11, 2011 an earthquake of magnitude 5.1 ( \(M_{w}\) ) struck Murcia region causing nine casualties and damage to buildings and infrastructures. Even if the main characteristics of the event would classify it as a moderate earthquake, the maximum Peak Ground Acceleration (PGA) registered (equal to 0.37 g) exceeded significantly local code provisions in terms of hazard at the site. This high PGA was a result of directivity effects in the near source region. An overview of earthquake characteristics and damage observed is provided. Notwithstanding the lack of proper structural design characterizing building stock in the area, most of the losses were caused by non-structural damage. According to in field observations, it emerges that masonry infills provided additional, “not designed”, strength to reinforced concrete (RC) buildings. Observed damage data, collected after the earthquake, are shown and compared to the results of a simplified approach for nonstructural damage assessment of RC infilled structures (FAST vulnerability approach). The latter comparison provided a fair accordance between observed data and analytical results.     

Ground motion characteristics and shaking damage of the 11th March 2011 M w9.0 Great East Japan earthquake

A catastrophic M _w9.0 earthquake and subsequent giant tsunami struck the Tōhoku and Kanto regions of Japan on 11th March 2011, causing tremendous casualties, massive damage to structures and infrastructure, and huge economic loss. This event has revealed weakness and vulnerability of urban cities and modern society in Japan, which were thought to be one of the most earthquake-prepared nations in the world. Nevertheless, recorded ground motion data from this event offer invaluable information and opportunity; their unique features include very strong short-period spectral content, long duration, and effects due to local asperities as well as direction of rupture/wave propagation. Aiming at gaining useful experience from this tragic event, Earthquake Engineering Field Investigation Team (EEFIT) organised and dispatched a team to the Tōhoku region of Japan. During the EEFIT mission, ground shaking damage surveys were conducted in Sendai, Shirakawa, and Sukagawa, where the Japan Meteorological Agency intensity of 6+ was observed and instrumentally recorded ground motion data were available. The damage survey results identify the key factors for severe shaking damage, such as insufficient lateral reinforcement and detailing in structural columns from structural capacity viewpoint and rich spectral content of ground shaking in the intermediate vibration period range from seismic demand viewpoint. Importantly, inclusion of several ground motion parameters, such as nonlinear structural response, in shaking damage surveys, can improve the correlation of observed ground motion with shaking damage and therefore enhance existing indicators of potential damage.     

Slope instabilities triggered by the 11th May 2011 Lorca earthquake (Murcia,Spain): comparison to previous hazard assessments and proposition of a new hazard map and probability of failure equation

The Lorca Basin has been the object of recent research aimed at studying the phenomena of earthquake-induced landslides and its assessment in the frame of different seismic scenarios. However, it has not been until the 11th May 2011 Lorca earthquakes when it has been possible to conduct a systematic approach to the problem. In this paper we present an inventory of slope instabilities triggered by the Lorca earthquakes which comprises more than 100 cases, mainly rock and soil falls of small size (1–100  \(\hbox {m}^{3}\) ). The distribution of these instabilities is here compared to two different earthquake-triggered landslide hazard maps: one considering the occurrence of the most probable earthquake for a 475-years return period in the Lorca Basin \((\hbox {M}_{\mathrm{w}}=5.0)\) based on both low- and high-resolution digital elevation model (DEM); and a second one matching the occurrence of the \(\hbox {M}_{\mathrm{w}}=5.2\) 2011 Lorca earthquake, which was performed using the higher resolution DEM. The most frequent Newmark displacements related to the slope failures triggered by the 2011 Lorca earthquakes are lower than 2 cm in both the hazard scenarios considered. Additionally, the predicted Newmark displacements were correlated to the inventory of slope instabilities to develop a probability of failure equation. The fit seems to be very good since most of the mapped slope failures are located on the higher probability areas. The probability of slope failure in the Lorca Basin for a seismic event similar to the \(\hbox {M}_{\mathrm{w}}\) 5.2 2011 Lorca earthquake can be considered as very low (0–4 %).     

Catastrophic Tohoku earthquake of March 11, 2011, in Japan

The results of the comparative analysis of parameters of the Tohoku earthquake (Honshu Island, Japan) of March 11, 2011, 05:46 UTC and its aftershocks are presented.     

Finite fault analysis and near-field dynamic strain and rotation estimates due to the 11/05/2011 (Mw5.2) Lorca earthquake,south-eastern Spain

The 11/5/2011 Lorca, Spain earthquake (Mw \(\,=\,\) 5.2) and related seismicity produced extensive damage in the town of Lorca and vicinity. During these earthquakes, evidence of rotations and permanent deformations in structures were observed. To analyze these aspects and study the source properties from the near-field, the displacement time histories were obtained including the static component at Lorca station. Displacement time histories were computed by an appropriate double time integration procedure of accelerograms. Using these data, the foreshock and mainshock slip distributions were calculated by means of a complete waveform kinematic inversion. To study the dynamic deformations, the 3D tensor of displacement gradients at Lorca station was first estimated by a single station method. Using the finite fault inversion results and by means of a first order finite difference approach, the dynamic deformations tensor at surface was calculated at the recording site. In order to estimate the distribution of the peak dynamic deformations, the calculation was extended to the close neighboring area of the town. The possible influence of the near-field deformations on the surface structures was analyzed.     

Ground shaking scenarios at the town of Vicoforte,Italy

Vicoforte is a small town in Northern Italy, which hosts a Cathedral with the world's largest elliptical dome. The name of the Basilica is “Regina Montis Regalis” and it is of extraordinary architectural and structural importance. The main objective of this study is the definition of the seismic hazard at the site of Vicoforte following a deterministic approach. Although Vicoforte is located in an area of moderate seismicity, the calculation of the most unfavourable seismic ground shaking scenarios is of great interest due to the importance of the Basilica and its vulnerability to even a moderate seismic excitation.The closest active faults to Vicoforte were identified in order to simulate the potentially most severe ground shaking scenarios compatibly with the tectonic and seismic setting of the region. Subsequently, numerical simulations were conducted through finite faults numerical models using two different approaches: the extended kinematic source model of Hisada and Bielak [24] and the stochastic method of Motazedian and Atkinson [38]. They, respectively, simulate the low and high frequency ranges of predicted ground motion. The numerical models used for the simulations were calibrated by a comparison between synthetic results and recorded data. A parametric study was finally carried out to identify the most critical fault rupture mechanisms.     

2011年日本大地震可能加速慢滑事件复发

相对于一般地震中快速的断层作用而言,慢滑(SSEs)是另一种形式的断层形变.人们在全球范围内的很多俯冲带板块边界观测到了这种短暂性滑动.位于日本中部的房总半岛(Boso Peninsula)附近的慢滑事件是记录最多的一个,拥有迄今为止最长的复发历史——将近30年,复发间隔为5～7年.     

Models for reproducing the damage scenario of the Lorca earthquake

A damage scenario modelling is developed and compared with the damage distribution observed after the 2011 Lorca earthquake. The strong ground motion models considered include five modern ground motion prediction equations (GMPEs) amply used worldwide. Capacity and fragility curves from the Risk-UE project are utilized to model building vulnerability and expected damage. Damage estimates resulting from different combinations of GMPE and capacity/fragility curves are compared with the actual damage scenario, establishing the combination that best explains the observed damage distribution. In addition, some recommendations are proposed, including correction factors in fragility curves in order to reproduce in a better way the observed damage in masonry and reinforce concrete buildings. The lessons learned would contribute to improve the simulation of expected damages due to future earthquakes in Lorca or other regions in Spain with similar characteristics regarding attenuation and vulnerability.     

On the GPS-based ionospheric perturbation after the Tohoku earthquake of March 11, 2011

Based on the data from the GPS receiving networks in Japan and America which have a high time resolution (2 min), two-dimensional (2D) distributions of the variations in the ionospheric total electron content (TEC) are constructed both close to and far from of the epicenter of the submarine earthquake of March 11, 2011 in Japan. Above the epicenter, a diverging multi-period disturbance appears after the main shock due to the acoustic gravity waves. Far from the epicenter, the wave trains associated with the tsunamigenic atmospheric internal gravity waves are revealed. These atmospheric waves significantly advance the arrival of the tsunami signal initially on the Hawaiian islands and then on the western coast of North America. The presence of the tsunami precursor in the form of atmospheric gravity waves is supported by the numerical calculations and by the analysis of the dispersion relation for the waves in the atmosphere. The detected ionospheric responses close and far from the epicenter can be used in the early tsunami warning systems.     

On the earthquake of March 11, 2011 near the northeastern coast of Honshu Island

The paper addresses the interpretation of the location, type, and size of the source for the earth-quake of March 11, 2011. The source—a subvertical reverse fault trending in the azimuth of ∼25° along the island arc—is located in the middle part of the Pacific slope of Honshu Island, between 38°–38.5°N and 35.5°N. The length of the source, about 350 km, approximately corresponds to a magnitude ∼8.7 earthquake. In the north, the source is bounded by a sublatitudinal reverse fault, which generated an earthquake with magnitude 7.2–7.5 in 1978. On this segment of the Pacific slope of Honshu Island, there are probably another one or a few other large seismic sources, which are still latent. They are longitudinal reverse faults, which are comparable in scale with the source of the March, 2011 earthquake. The recurrence period of the maximal earthquakes in such sources is more than 1000 years.     

2011 年云南盈江MS 5. 8 地震序列重定位

利用云南数字地震台网和腾冲火山台网记录的2011 年1 ～ 12 月震相数据,采用Hypo2000、HypoDD 定位方法对2011 年盈江MS5. 8 地震序列的前震、余震进行了重新定位。定位结果显示地震分布较定位前更为集中。前震活动主要沿大盈江断裂呈NE 走向分布。余震呈共轭分布:一支沿大盈江断裂呈NE 向分布,另一支沿垂直于大盈江断裂的隐伏错断呈SSE向分布。余震分布存在着稀疏段落,可能对应着前震主要破裂区域。     

The response of the electromagnetic field to the catastrophic earthquake of March 11, 2011

The electric and magnetic variations observed during the earthquake of March 11, 2011 that occurred in the Pacific close to the northeastern coast of Honshu Island in Japan are analyzed. The variations in the electric voltage were measured at the decommissioned submarine telecommunication cable laid on the bed of the Sea of Japan. The neighboring observatories recorded the anomalous geomagnetic variations during the studied time interval; the sources and spatial location of these anomalies are studied. The seismic signals were identified from the seismograms recorded by the broadband seismometer STS-2 at the nearest seismic station.

     

The response of the electromagnetic field to the catastrophic earthquake of March 11, 2011

The electric and magnetic variations observed during the earthquake of March 11, 2011 that occurred in the Pacific close to the northeastern coast of Honshu Island in Japan are analyzed. The variations in the electric voltage were measured at the decommissioned submarine telecommunication cable laid on the bed of the Sea of Japan. The neighboring observatories recorded the anomalous geomagnetic variations during the studied time interval; the sources and spatial location of these anomalies are studied. The seismic signals were identified from the seismograms recorded by the broadband seismometer STS-2 at the nearest seismic station.     

Observations on the building damages after 19 May 2011 Simav (Turkey) earthquake

An earthquake with a magnitude of 5.7 $(\text{ M}_{\mathrm{L}})$ has struck Simav, Kutahya located in the western part of Turkey on May 19, 2011. The ground motion caused observable damage within 25 km radius from the epicenter. Although the earthquake is moderate, its effects on the structures are serious. This paper presents the observations on seismic damages of reinforced concrete (RC) and masonry structures. Common reasons of damage in RC buildings are: low quality of concrete, detailing mistakes of reinforcement, short column, pounding, overhangs and misconstructed gable and outer infill wall parts. Interesting cases related to these deficiencies are reported. Damages in the masonry buildings are due to lack of connection between orthogonal walls and unsuitable location and dimension of openings. The damages at structures are more noticeable at regions with unfavorable soil conditions like plain regions or foothills. However, on stiffer soils at hilly sides, the damages seem to be more limited and masonry structures are observed to be less affected compared to the RC ones. The damages in RC buildings found to be increasing with story number for light damage states. However, for heavier damage states, 4–5 story buildings are observed to be the most damaged.     

Low frequency seismic noise before a magnitude 9.0 Tohoku earthquake on March 11, 2011

The dynamics of seismic noise before the catastrophic earthquake of March 11, 2011 in Japan is studied in a minute period range using the records of broadband IRIS stations. It is found that the dispersion of the noise and the number of asymmetric pulses recorded within 500 km from the epicenter of the earthquake have drastically increased 1.5 months before the event. This is the highest enhancement ever recorded by these stations during the same interval of the year for the past 15 years since the IRIS network started stably operating. No increase is revealed in the noise recorded beyond 1200 km from the epicenter. The pattern of decay in amplitudes of the anomalous noise with increasing distance from the epicenter to the corresponding stations likely indicates that the sources of the noise were located close to the source of the earthquake. The noise contains both regular and chaotic components.     

新疆塔什库尔干MS 5.5地震前兆异常分析

利用地震地磁分析方法及形态分析方法,分析2017年5月11日新疆塔什库尔干M_S 5.5地震前兆资料异常特征。结果表明：喀什地磁和伽师55井深层水温均出现明显的短期异常变化,主要表现为：①喀什地磁垂直分量逐日比、加卸载响应比均出现超限的高值异常;②中国大陆地磁台站在此次塔什库尔干M_S 5.5地震前出现低点位移突变分界线;③伽师55井深层水温出现弯曲型低值异常。