Lorca Earthquake Research Articles

Comportamiento, para el terremoto de Lorca de 11-05-2011, de edificios de vigas planas proyectados sin tener en cuenta la acción sísmica

The recent earthquake in Lorca (11-05-2011) was the most destructive recorded event in Spain, despite its moderate magnitude. This paper describes the numerical simulation of the dynamic response to the main record of the Lorca earthquake of six 3 and 6-story buildings with one-way concrete slabs with wide beams; these buildings were designed without any seismic consideration. We have chosen this type of construction because it is potentially highly vulnerable. The six considered buildings were selected to represent a large number of buildings of this type in areas of low-to-medium seismicity (as Lorca) of Spain along the period 1974-1994. The results show that these buildings, even with the cooperation of the walls, do not have sufficient capacity to withstand the most severe component of the Lorca record.

Foreword special issue LORCA’s earthquake

(This is an excerpt from the content) On May 11 2011 at 1705 hours, a small 4.5 Mw. magnitude earthquake struck the town of Lorca in south-eastern Spain. Other than alarmed citizens, only minor damage to buildings occurred due to this quake. Unfortunately at 1847 hours, a second shock registering a magnitude of 5.1 Mw. and very shallow (just around 2 km under the city) produced the largest seismic catastrophe registered in Spain in the last 120 years. This second shock is commonly referred to as “Lorca’s earthquake” and the following papers describe the context, circumstances and consequences of the event. Spain is a country of moderate seismic hazard in a global context. Before the Lorca earthquake, the most destructive earthquake in modern times was the so-called “Andalusian earthquake” (25th December 1884) that resulted in 750 fatalities and more than 1,500 injuries, reaching X in Mercalli’s intensity scale. Despite the lack of catastrophic events in the last 120 years, Spain has always had a scientific interest in seismic ...

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.

Detection of ionospheric signatures from GPS-derived total electron content maps

AbstractThe processing of measurement data from satellite constellations such as Global Navigation Satellite Systems (GNSS), including the well-known Global Positioning System (GPS), have been successfully applied to virtually all areas of geophysical sciences. In this work, a method is described where Geographical Information Systems (GIS) are employed to build hourly ionospheric Total Electron Content (TEC) maps for 2011 over the southern Iberian Peninsula. The maps used GPS-derived geometryfree linear combinations attained from station data from the Algarve, Alentejo (Portugal), Andalusia, Murcia and Valencia (Spain) regions. Following the construction of the ionospheric maps, it was possible to relate these results to natural phenomena. The observed phenomena included diurnal and seasonal variations: daytime TEC maxima, nighttime TEC peaks, summer TEC value decreases, and spring and fall TEC maxima. After validation of these periodic phenomena, detection of non-periodic changes, such as solar flares and tectonic interactions with the ionosphere were attempted. The results showed a TEC increase following a selected solar flare event and a potential TEC build-up prior to the 2011 Lorca earthquake. Further studies could open up the possibility of building early warning systems. The presented methods, based on available software packages, are also of value in monitoring the effect of the ionosphere on radio signals, satellite and mobile communication, power grids, and for accurate GNSS navigation.

Trastorno de estrés postraumático en escolares tras el terremoto de Lorca (España) en 2011

ObjectiveTo determine the prevalence of post-traumatic stress disorder (PTSD) in children after the 2011 earthquake in Lorca (Spain). MethodsBy using a cross-sequential design, children aged from 8 to 12 years (495 students at 1 month and 374 at 1 year) were assessed for full and partial PTSD using the Post-traumatic Children's Symptoms Stress Disorder Scale. ResultsThe percentage of children with PTSD was 55.4% (65.6% of girls and 46.9% of boys) at 1 month and 40.1% (44.5% girls and 35.9% children) at 1 year. One in two young girls (8-10 years) had PTSD 1 year after the earthquake. DiscussionA differential effect was observed due to gender and age, in which younger children, especially girls, were particularly at risk, even 1 year after the earthquake.

Tectonic setting of the recent damaging seismic series in the Southeastern Betic Cordillera, Spain

In this work we analyze the tectonic setting of the recent damaging seismic series occurred in the Internal Zones of the eastern Betic Cordillera (SE Spain) and surrounding areas, the tectonic region where took place the 11th May 2011 Mw 5.2 Lorca earthquake. We revisit and make a synthesis of the seven largest and damaging seismic series occurred from 1984 to 2011. We analyze their seismotectonic setting, and their geological sources under the light of recent advances in the knowledge on active faults, neotectonics, seismotectonics and stress regime, with special attention focused on the Lorca Earthquake. These seismic series are characterized by two types of focal mechanisms, produced mainly by two sets of active faults, NNW–SSE to NNE–SSW small (no larger than 20–30 km) extensional faults with some strike slip component, and E–W to NE–SW large strike slip faults (more than 50 km long) with some compressional component (oblique slip faults). The normal fault earthquakes related to the smaller faults are dominant in the interior of large crustal tectonic blocks that are bounded by the large E–W to NE–SW strike-slip faults. The strike slip earthquakes are associated to the reactivation of segments or intersegment regions of the large E–W to NE–SW faults bounding those crustal tectonic blocks. Most of the seismic series studied in this work can be interpreted as part of the background seismicity that occurs within the crustal blocks that are strained under a transpressional regime driven by the major strike slip shear corridors bounding the blocks. The seismotectonic analysis and the phenomenology of the studied series indicate that it is usual the occurrence of damaging compound earthquakes of M $$\sim $$ 5.0 associated with triggering processes driven by coseismic stress transfer. These processes mainly occur in the seismic series generated by NNW–SSE to NNE–SSW faults. These mechanical interaction processes may induce a higher frequency of occurrence of this kind of earthquakes than considered in traditional probabilistic seismic hazard assessments and it should be taken into account in future seismic hazard assessments.

Assessment of expected damage on buildings subjected to Lorca earthquake through an energy-based seismic index method and nonlinear dynamic response analyses

The city of Lorca (Spain) was hit on May 11th, 2011, by two consecutive earthquakes of magnitudes 4.6 and 5.2 M $$_\mathrm{w}$$ , causing casualties and important damage in buildings. Many of the damaged structures were reinforced concrete frames with wide beams. This study quantifies the expected level of damage on this structural type in the case of the Lorca earthquake by means of a seismic index $$I_{v}$$ that compares the energy input by the earthquake with the energy absorption/dissipation capacity of the structure. The prototype frames investigated represent structures designed in two time periods (1994–2002 and 2003–2008), in which the applicable codes were different. The influence of the masonry infill walls and the proneness of the frames to concentrate damage in a given story were further investigated through nonlinear dynamic response analyses. It is found that (1) the seismic index method predicts levels of damage that range from moderate/severe to complete collapse; this prediction is consistent with the observed damage; (2) the presence of masonry infill walls makes the structure very prone to damage concentration and reduces the overall seismic capacity of the building; and (3) a proper hierarchy of strength between beams and columns that guarantees the formation of a strong column-weak beam mechanism (as prescribed by seismic codes), as well as the adoption of counter-measures to avoid the negative interaction between non-structural infill walls and the main frame, would have reduced the level of damage from $$I_{v}$$ $$\,=\,$$ 1 (collapse) to about $$I_{v}$$ $$\,=\,$$ 0.5 (moderate/severe damage).

Revisiting the shallow Mw 5.1 Lorca earthquake (southeastern Spain) using C-band InSAR and elastic dislocation modelling

Space geodetic techniques such as interferometric synthetic aperture radar (InSAR) and global positioning systems (GPS) have demonstrated to be useful in mapping the displacement fields of large earthquakes (moment magnitude (Mw) ∼6 or higher). However, the displacement fields of smaller earthquakes (Mw < 5.5), such as those that typically result from the collision of the European and African plates, are less often analysed by space geodetic techniques, and their characterization, in terms of slip along the fault plane at depth and focal depth location, often challenges current seismological techniques. This letter presents the results of InSAR analysis of the 11 May 2011, Mw 5.1, Lorca earthquake. The Lorca earthquake occurred close to an area undergoing rapid subsidence due to sediment compaction related to water pumping. Therefore, it is challenging to separate the InSAR signals due to the earthquake from those due to human activity. We used four sets of SAR data acquired from the European C-band Advanced SAR (ASAR) sensor on board the Environmental Satellite (ENVISAT) to map the surface-displacement field in the Lorca region. Then, we use a simple elastic dislocation model to characterize the fault plane geometry and the fault slip at depth. We find that the InSAR signals can be explained by ∼21 cm reverse slip with a ∼6 cm left-lateral component on a 3 km × 3 km segment centred at 4.2 km depth dipping 45° NW and striking N65° E, consistent with the rupture of a segment of the Alhama de Murcia fault and consistent with recent published analyses. Interestingly, the InSAR signal can also be explained by ∼21 cm reverse slip with a ∼6 cm left-lateral component on a 3 km × 3 km segment centred at ∼4.2 km depth dipping 50° SE and striking N230° E, consistent with preliminary focal plane solutions indicating a rupture on a previously unmapped blind structure. We conclude that the second model cannot be rejected on the base of the InSAR results, the complex surface-displacement pattern (containing both seismic and non-seismic displacement), the different preliminary moment tensor solutions and the published locations of aftershocks at depth.

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 %).

Crustal deformation in eastern Betics from CuaTeNeo GPS network

The eastern Betic Cordillera, Spain, is the most seismically active area within the Iberian Peninsula. We present a Global Positioning System (GPS)-derived horizontal crustal deformation obtained from five occupations of the CuaTeNeo GPS network (1997, 2002, 2006, 2009 and 2011) that clearly shows continuing tectonic activity in the SE Betics. The most prominent feature of the GPS velocity field is the NW oriented motion of the majority of the stations at rates ranging from 2 mm/yr near the coast to 0.5 mm/yr inland. This type of deformation indicates that the main driving force responsible for the observed velocities is related to the on-going convergence between Nubia and Eurasia plates. The calculated deformation field shows evidence for localized deformation related to active faults within the area. Most of the deformation is concentrated on the Alhama de Murcia fault, the source of the 2011 Lorca earthquake (M w 5.2). We estimate a reverse-sinistral geodetic slip rate of 1.5 ± 0.3 mm/yr for this fault. Our crustal deformation field and analyses are important contributions to estimating seismic hazard for the eastern Betics, since it is the first time crustal deformation rates at this scale are presented. • Plate tectonics responsible for the deformation in the eastern Betics. • Calculated GPS crustal deformation rates range between 0.7 and 2 mm/yr to the NW. • The most active tectonic fault is Alhama de Murcia (1.5 mm/yr).

Characteristics of observed strong motion accelerograms from the 2011 Lorca (Spain) Earthquake

The Lorca earthquake (southeast Spain) on May 11, 2011; Mw 5.1, and its aftershocks, have provided an important set of accelerograms recorded by the strong motion network of the Instituto Geografico Nacional of Spain. It is particularly noticeable that the record obtained in Lorca town, very near of the fault rupture, presents a PGA value close to 0.37 g in the N30W component. This paper provides an overview of the strong motion data recorded during the Lorca seismic series, with particular attention to the accelerograms from the mainshock and foreshock and its characteristics. Due to the special circumstances of these two records, a more detailed processing has been required, in which various alternatives to adjust the baseline have been considered and analyzed. Based on this special processing, small residual displacements were obtained and reported in some of these cases. However, given the sensitivity of the process and the small obtained values, these findings should be taken with caution. Besides, response spectra have been analyzed and compared with design spectra proposed by the Spanish Seismic Code (NCSE-02) for the towns of Lorca, Alhama de Murcia and Mula. Large amplitude differences were observed in these spectra if compared to those recorded in Lorca. Also noteworthy is that the design spectra proposed for this town were exceeded by some horizontal directions of the response spectra.

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.

Characterization of earthquake shaking severity in the town of Lorca during the May 11, 2011 event

Exceptional ground motions have been observed in the near-source region in relatively small and moderate earthquakes such as the Lorca earthquake of 2011. In the Mw 5.2 mainshock, horizontal peak ground acceleration reached 0.37 g at the LOR accelerograph station in the north-central part of the town. Maximum ground acceleration and velocity in this station was strongly polarised in the fault’s strike-normal axis, a feature interpreted as a near-field effect of rupture directivity. This quake hit the Lorca area causing serious structural damage, unevenly distributed in the urban area as result of a heterogeneous spread of building vulnerability and seismic shaking severity. This study investigates the characteristics of the earthquake shaking at the LOR station (on rock) and other 11 zones of Lorca with different site conditions. We have computed the 1-D transfer functions of the shallow structure at these 11 points with available local Vs models obtained with SPAC technique. These transfer functions were used to convolve the LOR accelerogram and simulate the ground motion which occurred at each site. A set of key engineering ground-motion parameters obtained here, indicate different shake levels at each site and all these values are clearly above the LOR station ones. These parameter values are in the range of typical expected values for European earthquakes with local intensity VIII. Their large values, especially those of acceleration response spectra and energy input spectra, more clearly for periods between 0.4 and 0.6 s, point out that the seismic demand has been quite high and help to explain the heavy damage spread on the town’s buildings.

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 (Mw5.2) 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.

Field observations and interpretation of the structural performance of constructions after the 11 May 2011 Lorca earthquake

On the 11th of May 2011, an earthquake of magnitude Mw=5.1 hit the city of Lorca in the southeast region of Murcia, Spain. The earthquake caused a significant amount of damage over a very large number of buildings. In this context, the proposed paper presents an overview of the damage that was observed over the course of a 2-day reconnaissance trip that took place 2weeks after the earthquake. After providing a general summary of the regional tectonic settings and seismicity, the performance of the constructions during the earthquake is addressed, focussing on the damage observed in both historical and recent constructions. The observed damage patterns and their extent are analysed and interpreted in light of the construction typologies that were found.

Un caso de estudio para la sismología GPS: el terremoto de Lorca

1 Hz GPS data recorded by the GNSS network of the Consejería de Agricultura y Agua of the Murcia Region during the Mw 5.1 Lorca earthquake on May 11th 2011 is used as a test case. A Precise Point Positioning (PPP) approach is applied to analyse the earthquake-induced motion of the station LORC, located close to the epicenter. The results are validated using a conventional Double Differences (DD) processing. After applying sidereal and regional filters, the detected transient motion is about 20 millimeters in each component and clearly above noise level. The results from the two different processings are compared in view of the accuracy and applicability. The PPP approach described here can potentially be used for real-time analysis e.g. based on NTRIP streaming data. It may be used to set up an early warning system, as well as to gain real-time knowledge of ongoing earthquakes, extending the already-existing seismic information obtained from classical measurements.

Deformación cortical de las Béticas Orientales observada mediante GPS y su relación con el terremoto de Lorca

On May 11 th of 2011, a seismic series occurred near the city of Lorca (Murcia). The main earthquake of magnitude Mw 5.2 has been attributed to the Alhama de Murcia Fault, one of the most active faults in the SE Iberian Peninsula. We analyzed data from 5 GPS campaigns of the CuaTeNeo network conducted between 1997 and 2011. The velocities of the stations closest to the Alhama de Murcia Fault show the reverse and strike-slip direction of motion. Stations located on the southeastern side of the fault have the maximum velocities in the area (between 1.4 and 1.8 mm/yr), oriented towards NNW direction, obliquely to the trace of the fault. The kinematics of the fault and the strain rate directions obtained from the CuaTeNeo network GPS measurements matches the calculated focal mechanism of Lorca earthquake. Detailed analysis of the time-series from the continuous GPS station at the Lorca city allows the detection of co-seismic offset of ~6 mm to the North.

El terremoto de Lorca (2011) en el contexto de la peligrosidad y el riesgo sísmico en Murcia.

An analysis of the different aspects related to the May 11th, 2011 Lorca earthquake is presented, covering recorded ground motions, damage observed in different building typologies, and contrasting these observations with previous results on seismic hazard and seismic risk obtained in the province of Murcia. The essential question addressed in the analysis is whether observed ground motions and physical damage can be considered as expected or as anomalous in the frame of seismic risk in southeastern Spain. In this respect, a number of reflections are carried out and several learned lessons from the earthquake are extracted, which leads to the proposal of different recommendations for the future revision of the Spanish earthquake-resistant provisions, as well as for defining risk reduction measurements in the region.

The 2011 Lorca earthquake slip distribution controlled by groundwater crustal unloading

Earthquake rupture is influenced by stress conditions in the crust before the quake. Analysis and modelling of surface deformation caused by the May 2011 earthquake in Lorca, Spain, indicate that groundwater extraction influenced the pattern of fault rupture.

Experiencias constructivas del terremoto de Lorca

El terremoto de Lorca del 11 de mayo de 2011 es el más importante que ha sufrido el territorio peninsular español en los últimos 55 años, desde el terremoto de Albolote (Granada) de 1956 que, casualmente, fue del mismo tipo y tuvo idéntica magnitud de 5,1 grados en la escala Richter. En estos 55 años, la tipología de los edificios ha cambiado completamente, pasando de edificios de muros de fábrica de hasta dos plantas de altura, a la generalización de edificios de pisos de una media de 6 plantas, de pilares y vigas con nudos rígidos y forjados de hormigón. Es importante extraer experiencias constructivas del comportamiento que han tenido los edificios de Lorca, porque es el único caso real de que disponemos, para la mejora de la seguridad estructural antisísmica de los edificios en España. En Lorca se ha constatado el mal comportamiento de las estructuras de fábrica de ladrillo con las que está construido el patrimonio histórico. Se ha probado que, con la sola excepción de un edificio, las estructuras nuevas de hormigón y acero han superado una aceleración sísmica del triple de la prevista por la norma sismorresistente NCSE-02, con la que fueron calculadas. Por el contrario, se ha constatado un pésimo comportamiento de los elementos de fábrica (petos, cerramientos, tabiques, etc, de ladrillo) con fracasos generalizados, que son los que produjeron los enormes daños materiales en las viviendas y los daños personales. Estos elementos no son «estructurales», pero la norma NCSE-02 establecía para ellos unas condiciones que no debieron aplicarse en las construcciones realizadas desde su implantación.