Lorca Earthquake Research Articles

Active Fault Interaction in the Eastern Betic Cordillera: A Model of Coseismic and Postseismic Stress Transfer Following Historical Earthquakes in SE Spain

AbstractThe Spanish historical earthquake catalog reveals a significant number of destructive earthquakes (Mw 6.0) that have occurred along the Eastern Betic Shear Zone (EBSZ), a major active fault system at the Eastern Betic Cordillera. However, during the last century, seismic activity in this region has been characterized by the absence of large‐magnitude events, complicating yet underlining the importance of understanding active fault interaction in the EBSZ. In this work, we focus on the northeastern half of the EBSZ and apply a similar method to Yazdi et al. (2023, https://doi.org/10.1029/2023tc007917). We model a series of consecutive earthquakes ( VII; Mw 5.0) between the and centuries occurring along the Alhama de Murcia, Carrascoy and Bajo Segura faults, and assess their coseismic impact as well as explore the evolution of Coulomb stress changes due to the postseismic viscoelastic relaxation on the surrounding faults. Our results support a stress‐triggering connection between subsequent events and shed light on identifying the responsible faults for some. Our findings indicate that 1673 Mw 6.0 Orihuela and 1674 Mw 6.2 Lorca earthquakes, seemingly unrelated, could have both contributed to the forthcoming Mw 5.0 earthquake clustering along the Carrascoy fault. We show that attributing the 1829 Mw 6.6 Torrevieja earthquake to the Bajo Segura fault better describes the occurrence of earthquake sequences between the mid‐ and early centuries. Finally, we propose the Alhama de Murcia and the Carrascoy faults as responsible initiators for the early ‐century earthquake sequence in the Segura Medio valley. These findings provide valuable insights for seismic hazard modeling in the region.

Flow-geomechanics coupling constrains fault geometry in induced earthquakes

Post-mortem analysis of earthquakes induced by fluid extraction or injection is often complicated by the uncertainty in the location and geometry of the causative fault. The 2011 Lorca earthquake in southeast Spain is believed to have been triggered by long-term groundwater withdrawal, causing slip along the Alhama de Murcia Fault (AMF) dipping northwest. However, the regional InSAR deformation data can be equally fit by AMF and an unmapped fault located approximately 5-8 km west of AMF and dipping southeast, which creates an ambiguity in the causative fault that hosted the earthquake. Here, we show that the assumptions of elastic dislocation, undrained deformation, and decoupling between flow and deformation processes contributed to the ambiguity, which can be resolved by conducting a fully coupled analysis that provides additional constraints on the problem. We test that hypothesis and propose that the Lorca earthquake was likely caused by the rupture of a southeast dipping fault plane, which is antithetic to AMF. We build a mechanistic model of groundwater withdrawal over the time period of interest (1960–2010) that includes pressure diffusion, aquifer contraction, crustal unloading, and basement expansion mechanisms. The model identifies the difference in production-induced loading of the two faults: AMF experiences poroelastic compression and down-dip shear whereas the antithetic fault experiences tension and up-dip shear. We demonstrate that two-way coupling between flow and deformation processes plays a crucial role in the natural selection of the causative fault. The proposed framework holds the potential to detect hidden faults capable of hosting earthquakes.

Vulnerability of reinforced concrete frames using anti-seismic hysteretic devices for the Lorca earthquake (2011)

Many buildings around the world are extremely vulnerable to serious and moderate earthquakes. Base isolation and energy dissipators are the traditional techniques in anti-seismic designs. The present paper focuses on the suitability of using hysteretic energy dissipators in braced buildings in low-to-medium seismic zones, such as southeast Spain. To this end, static (Push-over) and dynamic analyses have been carried out using the record of the Lorca earthquake (2011) in its most unfavorable direction (N-S), using reinforced concrete frames of low (5 stories frame), medium (10 stories frame), and high height (15 stories frame) with hysteretic dissipators (based on metal plasticization) and economical and easy-to-use devices. The results show that this type of solution is appropriate in the case described and indicate the advantages and disadvantages of its use in buildings in the study area. The results show that the effectiveness of the dissipative devices increases with the height of the frames, in terms of displacements, resistance, and distribution of moments in the primary structural elements of the frames (beams and columns).

Constraining earthquake fault sources through the use of intensity data and seismic scenarios: application to the Betic Cordillera (South Spain)

Macroseismic observations can be useful to study pre-instrumental earthquakes when paleoseismological analysis are not viable for various reasons (e.g., erosion or lack of sedimentation). The analysis of the distribution of the macroseismic intensity data points and the reports about geological effects has been shown as a tool that may provide meaningful information to localize the fault source of a historical earthquake. Using this approach, we have studied two earthquakes in the Betic Cordillera (South Spain), the 1804 Dalías and the 1680 Málaga events, and we have used the 2011 Lorca earthquake as a test subject to calibrate the methodologies. During the calibration process, we also find the best performing combination of ground-motion models and ground-motion-to-intensity-conversion equations for generating seismic scenarios in this area. Even though the results for the Málaga earthquake were not conclusive, our methodology successfully identified the most likely source for the Dalías earthquake: a conjunct rupture of the Loma del Viento and Llano del Águila Faults.

Comparison between Machine Learning and Physical Models Applied to the Evaluation of Co-Seismic Landslide Hazard

A comparative methodology between advanced statistical tools and physical-based methods is carried out to ensure their reliability and objectivity for the evaluation of co-seismic landslide hazard maps. To do this, an inventory of landslides induced by the 2011 Lorca earthquake is used to highlight the usefulness of these methods to improve earthquake-induced landslide hazard analyses. Various statistical models, such as logistic regression, random forest, artificial neural network, and support vector machine, have been employed for co-seismic landslide susceptibility mapping. The results demonstrate that machine learning techniques using principal components (especially, artificial neural network and support vector machine) yield better results compared to other models. In particular, random forest shows poor results. Artificial neural network and support vector machine approaches are compared to the results of physical-based methods in the same area, suggesting that machine learning methods can provide better results for developing co-seismic landslide susceptibility maps. The application of different advanced statistical models shows the need for validation with an actual inventory of co-seismic landslides to ensure reliability and objectivity. In addition, statistical methods require a great amount of data. The results establish effective land planning and hazard management strategies in seismic areas to minimize the damage of future co-seismic landslides.

Extending urban seismic risk assessment to open spaces for the 2011 Lorca earthquake scenario

Extending urban seismic risk assessment to open spaces for the 2011 Lorca earthquake scenario

NSE seismic demand characterization: the case of a Spanish RC residential building

In reinforced concrete buildings, non-structural elements (NSE), such as masonry infills and parapets, constitute the cause of a considerable number of fatalities and huge economic losses in developed countries, in the case of medium magnitude earthquakes (4-6 Mw). As an example, during the 5.2Mw 2011 Lorca (Spain) earthquake, falling debris from unreinforced masonry NSE gave rise to the nine fatalities incurred. The majority of these elements were located in 4 to 6-storey reinforced concrete residential buildings. Within this framework, this contribution addresses the characterization of the seismic demand of NSE through the study of the response of a building in Lorca pertaining to the described structural type, by means of the Floor Response Spectra (FRS) method. For this purpose, the infilled frame model was created in SAP2000 with masonry infills simulated by equivalent struts. The infilled frame model is calibrated so as to fit with the main elastic period of the building, identified by means of ambient vibration tests conducted with a Tromino device. The FRS results obtained with the numerical model by a Linear Time-History (THA) analysis simulating the Lorca earthquake, are compared with the results suggested by the Eurocode in force and by the Italian Building Code. Specifically, in the case of the Italian Building Code, both the simplified formulation for moment resisting frame buildings and the modal superposition spectrum-to-spectrum approaches are considered. Finally, the potential resonance of the dynamic behaviour between the obtained FRS and the natural periods of the masonry parapets located at the top of the building is discussed.

Reproduction of and alterations in gender roles in the rescue of material goods after the 2011 earthquake in Lorca (Spain)

ABSTRACT After a disaster, the population undertakes a series of actions aimed at saving and rescuing other people who may be in danger, as well as the gathering of goods considered indispensable to ensure their safety. Numerous studies have indicated that gender is one of the factors that conditions the lived experience of a disaster and, therefore, the actions that people undertake during the emergency. However, previous studies addressing the issue of gender in this respect have focused on how people are evacuated from the danger area, rather than on the rescue of goods. With the aim of contributing to filling this gap, the current article studies the patterns of the reproduction of/alteration in gender roles in the rescue of material goods following the earthquake in Lorca (Spain) in 2011 through the analysis of raw data collected from four focus groups comprising people who survived this catastrophic event. The results demonstrate that during the rescue actions in the disaster the men and women studied behaved to a great extent in line with traditional gender roles, although there were certain actions undertaken that involved a degree of alteration to these roles.

Women and children first? An analysis of gender roles in the rescue of people following the 2011 Lorca earthquake

Catastrophes like earthquakes, hurricanes and tsunamis, have a devastating effect which extends beyond personal or material losses and also affect social order. At the same time, there is an increasing amount of scientific evidence demonstrating the impact of disasters on gender relations. This article aims to investigate an issue that to date has not been examined in the Spanish context, namely the gender roles undertaken by men and women in the rescue of people after a catastrophe has occurred. To this end, the discourse from four focus groups of people who experienced the 2011 earthquake in Lorca (Spain) has been analysed. The focus groups were recorded, transcribed and codified with the MAXQDA program and afterwards an interpretative analysis was carried out.The results of this study demonstrate that, although, in principle, the danger should be the same, the lived experiences and reactions of men and women faced with a catastrophic event are often different. Men appear as the principal protagonists of the rescue phase and their way of rescuing as the norm. Despite the fact that women also play an active role in saving people, their protective actions are less visible. In part this is because women do not limit their actions to physical rescue, but also make suggestions and recommendations aimed at helping people around them and often remain with those who are rescued. These findings point to the need to broaden the notion of what rescue involves through incorporating the specific actions of women identified.

Experimental and analytical assessment of the influence of masonry façade infills on seismic behavior of RC frame buildings

On May 11, 2011 at 6:47p.m., an M5.1 earthquake took place in Lorca at a depth of 4 km, in the Region of Murcia, south of Spain, which resulted in nine fatalities and 324 injuries and major built environment damage. Approximately 80% of the residential buildings were affected with various degrees of damage, 5% with severe structural damage and 13% with moderate structural damage, in addition to the damage of infrastructure and public buildings. Reconnaissance and expert analyses revealed that one of the main causes of damage during the Lorca earthquake was the interaction between the non-structural elements and the seismic-resisting framing of the buildings. Studies on this interaction, that started in the 1950 s, led to the development of a wide range of macro-models that simulate the stiffness of the masonry infills using one or more equivalent diagonal strut(s). Following an extensive literature review, 12 mathematical expressions have been compiled to estimate the horizontal stiffness of the equivalent strut that simulates the behavior of masonry infills that make up a typical façade of many modern buildings. Two full-scale tests under horizontal cyclic displacement reversals have been carried out on two 5x3m concrete frames: one frame with masonry infill simulating a regular façade; and the other is a bare control frame. The comparison of both tests enabled quantifying the stiffness contribution of the façade infill and identifying the simplified expression that best fits the horizontal stiffness. Using this expression, a realistic seismic design of a prototype building in Lorca, Spain, is conducted under the typical assumption of most modern building codes to consider masonry infills as non-structural elements, and consequently the designed building was seismically assessed considering the influence of the infills. Results of the assessment are in accordance with the real damage patterns observed during the Lorca earthquake reconnaissance.

Women and Children First? An Analysis of Gender Roles in the Rescue of People Following the 2011 Lorca Earthquake

Women and Children First? An Analysis of Gender Roles in the Rescue of People Following the 2011 Lorca Earthquake

Specific seismic retrofitting of a compact reinforced concrete building with X-bracings and steel jackets. Application to a primary school in Huelva.

Previous research has indicated that many European buildings are vulnerable to moderate-magnitude earthquakes. For example, during the L´Aquila (Italia, Mw 6.3, 2009) and Lorca (Spain, Mw 5.9, 2011) earthquakes, many old buildings were severely damaged and some of them collapsed. In specific, significant damage has been found in several school buildings after past earthquakes in Europe. This is due to the fact that many of them were constructed prior to the current seismic codes, thus considering only gravitational loads and with no seismic design whatsoever. Primary schools are even more vulnerable than other typologies because of their low adult/child ratio. The seismic activity of the Iberian Peninsula is low-moderate. However, the Algarve and Huelva regions, which are situated in the south-west, are influenced by large faults which have caused major earthquakes of long-return periods. The European project PERSISTAH (Projetos de Escolas Resilientes aos SISmos no Território do Algarve e de Huelva, in Portuguese) aims to cooperatively evaluate the seismic vulnerability of primary schools in the Algarve (Portugal) and Huelva (Spain) regions. The present work is framed under this project. The objective of this paper is to determine the most effective retrofitting scheme for a typical primary school building in this area, considering structural, architectural and constructive parameters. The scheme could be applied to several buildings of the same typology, decreasing costs and time. An existing reinforced concrete frame building has been selected for the study. This is one of the most commonly used typologies for primary schools in this area. A nonlinear static analysis has been carried out in order to study its seismic behaviour. The performance point of the building has been obtained through the capacity-demand spectrum method. The preliminary results have confirmed the poor seismic behaviour of this building. Specifically, soft-story behaviour has been identified in the ground floor and short columns have been observed in the upper floors. Therefore, specific seismic retrofitting solutions have been proposed and evaluated in order to identify the one that is the most efficient. The combination of reinforcements has been done considering the structural and architectural impact and constructive parameters. The calculations have shown that steel X-bracings are the best solution for preventing the formation of a soft-storey in the ground floor. Unfortunately, this scheme increases the deformation in the upper floor columns. The best solution for the upper floors' short columns has been the use of steel jackets. The results have also shown that this combination produces an important reduction of the expected general damage level. The resulting retrofitting scheme can be extrapolated to other buildings with a similar typology.

Assessing Building Habitability after an Earthquake Using Building Typology and Damage Grade. Application in Lorca, Spain

ABSTRACT The present study proposes a statistical methodology to rate the habitability of different types of buildings after an earthquake. The first step was to rank variables that affect the vulnerability of a building and formulate a statistical study with a discrimination index that makes it possible to identify buildings as habitable or non-habitable. This ranking applied the criteria established in various international guidelines that are used to distinguish between habitable (undamaged/no structural damage) and non-habitable buildings (structural damage). The proposed methodology was applied to a database with information about buildings and damage grade experienced following the 2011 earthquake in Lorca. The approach presented could be extended to other regions where neccessary data are available.

Obtaining suitable logic-tree weights for probabilistic earthquake-induced landslide hazard analyses

In this study, an inventory of landslides induced by the 2011 Lorca earthquake (Mw 5.1) has been used in order to develop a new procedure to obtain objective logic-tree weights for a probabilistic earthquake-induced landslide hazard analysis. The 2011 Lorca earthquake triggered more than 250 landslides, mainly of disrupted type. The logic-tree was designed having regard to variability of relevant geotechnical parameters involved in the problem and uncertainties associated with the use of several empirical relationships in order to compute Newmark displacements. For the purpose, the resulting hazard maps were compared with this landslide inventory, and weights estimated for each branch of the logic tree based on these results. The best model for seismic landslide hazard mapping for a moderate earthquake correctly identifies around 72% of landslide areas. Based on the set of parameters that comprises (depth of failure surface, specific weight, cohesion, friction angle and Newmark displacement model), the corresponding weights were objectively established. These weights are reliable enough for the obtaining seismic landslide hazard maps and may be implemented in similar environments characterized by moderate-low magnitude earthquakes (Mw < 5.5).

Dynamic Monitoring of a Mid-Rise Building by Real-Aperture Radar Interferometer: Advantages and Limitations

In this paper, remote and in situ techniques to estimate the dynamic response of a building to ambient vibration are reported: data acquired through a real-aperture radar (RAR) interferometer and conventional accelerometers are analyzed. A five-story reinforced concrete housing building, which was damaged during the May 11th 2011 Lorca (Spain) earthquake, is used as a case study. The building was monitored using both types of instruments. The dynamic properties of the building are estimated first taking acceleration measurements using a set of 10 high-precision accelerometers installed on the roof of the building. Further, the displacement–time histories, recorded with the RAR device pointing to a corner of the building, are analyzed. Then, the ability and shortcomings of RAR measurements to deal with the fundamental frequencies of vibration of the structure are investigated. The advantages and limitations of from-inside (accelerometric) and from-outside (RAR) measurements are highlighted and discussed. A relevant conclusion is that, after strong earthquakes, RAR may be an interesting and useful tool, as it allows surveying the structural response of mid-rise buildings remotely, without the need to enter the structures, which may be dangerous for inspectors or technicians in cases of severely damaged buildings. Given that the instrumented building suffered significant damage, the ability of these kinds of measurements to detect damage is also discussed.

Magnetotelluric characterization of the Alhama de Murcia Fault (Eastern Betics, Spain) and study of magnetotelluric interstation impedance inversion

The Lorca earthquake (May 11th, 2011, Mw 5.2) stands as the most destructive one in Spain over the last 50 years, interpreted as having occurred in an intersegment zone of the strike–slip Alhama de Murcia Fault (AMF) (Eastern Betics, Spain). Magnetotelluric data were acquired along a profile to the SW of Lorca (La Torrecilla profile), to characterize its signature at depth, as part of the multidisciplinary project “INTERGEOSIMA”. Given the short distance between stations, some station pairs were recorded simultaneously, with magnetic sensors in only one of them. In order to properly understand the resulting impedances (called interstation impedances), and the effects of inverting them, we used synthetic models to compare the impedances and the interstation impedances and to analyze the corresponding inversion results, together with the inversion of the quasi-impedance (inversion of the interstation impedances, considering them as impedances). The results are sensitive to the location of the magnetic sensors and the resistivity underneath, but in general the use of the quasi-impedances in the inversion can be considered a valid procedure. Both the 2D and the 3D resistivity models obtained through the inversion allowed us to complement the previous ERT models and represent the continuation of the main fault gouge in depth showing its extension towards the SE.

Assessment of Post-Earthquake Damaged Building with Interferometric Real Aperture Radar

In this study the main results of a detailed analysis of an actual building, which was severely damaged during the Mw 5.1, May 11th 2011, Lorca earthquake (Murcia, Spain) are presented. The dynamic behavior of the building was analyzed by means of empirical and numerical approaches. The displacement response of the building submitted to ambient noise was recorded by using a Real Aperture Radar (RAR). This approach provides a secure remote sensing procedure that does not require entering the building. Based on the blueprints and other available graphical information about the building, a numeric 3D model was also set up, allowing obtaining capacity spectra and fragility curves in the two main resistant directions of the building. The main purpose of this study was to check out the feasibility of the RAR-based method to detect the safety state of a damaged building after an earthquake, without the need of entering unsafe structures. A good consistency of the numerical and experimental approaches and the observed damage was obtained, showing that RAR interferometric-based tools may provide promising supplementary remote sensing methods to safely survey and report about the structural health and the operative conditions of buildings in post-earthquake scenarios.

Modification of the risk of post-traumatic stress disorder (PTSD) by the 5-HTTLPR polymorphisms after Lorca's earthquakes (Murcia, Spain).

Information of the modulation effect of the serotonin transporter gene-linked polymorphic region (5-HTTLPR) on post-traumatic stress disorder (PTSD) after earthquakes is scarce and contradictory. A cross-sectional face-to-face interview survey of a representative sample of the adults was carried out after the Lorca (Spain) earthquakes (May 11, 2011). Socio-demographic variables, DSM-IV diagnostic assessment and earthquake-related stressors were obtained from the Composite International Diagnostic Interview (CIDI). The triallelic and biallelic classification of the 5-HTTLPR polymorphism were genotyped from buccal swabs.Multivariate logistic regression models were used to predict PTSD, including interaction terms to explore gene-environment (G x E) interactions. The vast majority (83%, n = 341) of the Lorca survey respondents (n = 412, 71% response rate) were genotyped. Both classifications of the 5-HTTLPR genotype were in Hardy-Weinberg equilibrium. Prior lifetime PTSD was the only variable that remained a significant predictor after adjustments. There were no significant main effects of earthquake related stressors or 5-HTTLPR. However, G x E interactions of 5-HTTLPR with high emotional impact and prior lifetime anxiety disorders were statistically significant. These results provide new evidence of the modulation effect of the 5-HTTLPR polymorphisms on PTSD risk. This information might characterize people at higher risk of developing PTSD after an earthquake exposure.

Editorial

Editorial

Using an Interferometric radar to assess post-earthquake damage status of an urban building: a case study

This paper reports the use of an interferometric radar to support the detection of the main vibrating frequencies of a building damaged after the Mw 5.1, May 11th 2011, Lorca earthquake (Southeast Spain). The surveyed building, a reinforced concrete structure, was located in the San Fernando neighbourhood of the city of Lorca, where the earthquake caused severe damages. The radar survey was carried out some months after the earthquake. To assess the building capacity and fragility, a pushover analysis has been carried out. The building has been modelled by using the SAP2000 software. The goal of the study is to detect changes of the main natural frequencies of a specific building after the earthquake and, through a comparison of the building frequencies before and after the earthquake, to estimate the effect of the earthquake on the monitored building.