Main crustal seismic sources in El Salvador

We present a map and a data set containing information about intra-plate seismic sources in El Salvador. These are the results of the field campaigns and data analysis carried out by the research group of Planetary Geodinamics, Active Tectonics and Related Risks from Complutense University of Madrid during the last 12 years. We include two maps, the first map contains 1405 fault traces with evidences of Quaternary activity derived form morphometric, paleoseismological and geomorphological analysis together with field data mapping carried in El Salvador. The second map is a synthesis of the 29 intra-plate seismic sources selected from the quaternary faults map. The geometry of these sources was simplified and we also include a table where some available data of the proposed sources are included, such as their name, orientation, length and slip-rate. For further interpretation and discussion of these sources see (Alonso-Henar et al., 2018) [1, doi.org/10.1016/j.enggeo.2018.06.015]This research was supported by the project“ QUAKESTEP”(CGL2017–83931-C3-1-P) founded by the Spanish Ministry of Science, Innovation and Universities. We are grateful to our colleagues atDGOA-MARN (Observatorio Ambiental del Ministerio de Medio Ambiente y Recursos Naturales de ElSalvador): Manuel Díaz, Walter Hernandez and Douglas Hernández for their assistance. Figures were produced using GMT softwar

Structural evolution of the El Salvador Fault Zone: an evolving fault system within a volcanic arc.

The El Salvador Fault Zone, firstly identifiedafter the 13th February 2001 Mw 6.6 El Salvador earthquake, is a 150 km long,20 km wide right-lateral strike-slip fault system. Ruptures along the ESFZ arethought to be responsible for most of the historical destructive earthquakesalong the El Salvador Volcanic Arc, as well as for most of the currentseismicity of the area. In this work, we focus on the geological setting of thefault zone by describing its geomorphology and structure, using field-based observations,digital terrain modelling, and aerial photograph interpretation with the aim atcontributing to the understanding of the ESFZ slip behaviour. In particular, weaddress the ESFZ structure, kinematics and evolution with time. The ESFZ is a complex set of traces divided inmajor rupture segments characterized by different geometry, kinematics andgeomorphic expressions. Natural fault exposures and paleoseismic trenchesexcavated along the fault show that the strike slip deformation is distributedin several planes. Both geometry and kinematics of the fault zone areconsistent with a transtensional strain regime.The estimated geological slip-rate for the mainfault segments by paleoseismic trenches and displaced geomorphic features impliesa deficit in velocity of the fault compared to the available GPS velocitiesdata. The high vertical scarps of some fault segments would require quaternaryslip rates not coherent neither with measured GPS velocities nor with sliprates obtained from paleoseismic analysis. This mismatch suggests apre-existing graben structure that would be inherited from the previousregional roll back related extensional stage. We consider that the ESFZ isusing this relict structure to grow up along it. As a result, we propose amodel for ESFZ development consistent with all these observations.La Zona de Falla de El Salvador (ZFES) es un sistema de falla de desgarre dextral de 150 km de longitud y 20 de anchura, que fue identificada por primera vez después del terremoto de Mw 6.6 de El Salvador de febrero de 2001. La mayoría de la sismicidad y de los terremotos históricos destructivos producidos en el arco volcánico salvadoreño han sido producidos por la ruptura de la ZFES. Este trabajo se centra en el marco geológico de la zona de falla describiendo su geomorfología y su estructura a través de observaciones de campo, del estudio de los modelos digitales del terreno y de la interpretación de las fotografías aéreas, con el objetivo de avanzar en el conocimiento del comportamiento de la ZFES. En concreto trataremos del estudio de la estructura, la cinemática y la evolución de la ZFES. La ZFES es un complejo sistema de fallas divididas en varios segmentos que se diferencian en la geometría, la cinemática y la expresión geomorfológica. En los afloramientos de la falla, así como en las trincheras paleosismicas excavadas se ha observado que la deformación de desgarre está distribuida en varios planos y tanto la geometría como la cinemática de la zona de falla indican que la ZFES está bajo un régimen de deformación transtensional. La tasa de deformación estimada para los principales segmentos a través del estudio paleosísmico y del análisis de indicadores geomorfológicos desplazados nos muestra un déficit de velocidad para la falla si lo comparamos con los datos obtenidos por GPS. Estos datos tampoco ayudan a explicar la existencia de grandes escarpes verticales que se observan en algunos segmentos de la falla, y que requerirían tasas de deformación muy elevadas. Esta discrepancia sugiere la existencia de una estructura de graben preexistente que puedo ser producida por el “roll-back” de la placa y que creó una fase extensional en el arco volcánico. En este trabajo consideramos que la ZFES está actualmente desarrollándose sobre la estructura extensional relicta y como resultado proponemos un modelo estructural consistente con estas observaciones

Paleoseismological evidence of Holocene activity of the Los Tollos Fault (Murcia, SE Spain): A lately formed Quaternary tectonic feature of the Eastern Betic Shear Zone

[EN] The Los Tollos Fault is a recent and important feature of the Eastern Betic Shear Zone, one of the major tectonic structures in South Iberia accommodating the convergence between Nubian and Eurasian plates in the western Mediterranean. The Los Tollos Fault became active by the end of Middle Pleistocene introducing some paleogeographical modifications. Previously mapped as a secondary normal fault related to the Carrascoy Fault, recent research evidences that the Los Tollos Fault is an independent Holocene active left-lateral reverse fault extending for at least 15 km. Data analysis from 4 trenches dug across the fault has revealed the occurrence of at least two paleo-earthquake events during the Holocene. The most recent event is dated between 2,740 and 2,140 yr BP (8th to 2nd centuries BC). The size of the paleoevents is calculated to be Mw 6.3 – 6.6 following empirical regressions on surface rupture length. The recurrence interval is estimated to be between 2,200-6,860 years, fitting a slip rate for the fault between 0.12 and 0.17 mm/yr. Such parameters highlight the Los Tollos Fault as a tectonic structure with a considerable activity located relatively close to densely populated areas. These seismogenic parameters should be considered in future reassessments of the seismic hazard of the region.[ES] La falla de Los Tollos es una estructura reciente e importante de la Zona de Cizalla de la Bética Oriental, la principal estructura del sureste de la Península Ibérica que acomoda gran parte de la convergencia entre las placas de Eurasia y Nubia en el Mediterráneo Occidental. La falla de Los Tollos, descrita inicialmente como una falla normal secundaria relacionada con la falla de Carrascoy, comenzó su actividad a finales del Pleistoceno Medio generando algunas modificaciones paleogeográficas significativas. El trabajo que aquí presentamos demuestra su activad durante el Holoceno con una cinemática lateral sinestral con componente inversa a lo largo de una longitud de 15 km, e independiente de la Falla de Carrascoy. Del análisis de los datos obtenidos en 4 trincheras paleosismológicas realizadas a lo largo de la traza de la falla, se han podido interpretar la ocurrencia de al menos 2 paleoterremotos durante el Holoceno, acotándose el evento más reciente entre hace 2.740 y 2.140 años (siglos VIII a II a.C.). La magnitud máxima de estos paleoterremotos, estimada mediante correlaciones empíricas que consideran la longitud de rotura en superficie de la falla, se encuentra entre Mw 6,3 y 6,6, con un periodo de recurrencia comprendido entre 2.200 y 6.860 años. La tasa de deslizamiento neta calculada para la falla se estima entre 0,12 y 0,17 mm/a. Estos parámetros identifican la falla de Los Tollos como una estructura activa situada en las cercanías de áreas densamente pobladas y ponen de manifiesto el interés que tendría considerarla en futuras reevaluaciones de la peligrosidad sísmica en la región.FASEGEO Project (CGL2009-09726) funded by the Spanish Ministry of Science and Innovation.Peer reviewe

Paleoseismological evidence of Holocene activity of the Los Tollos Fault (Murcia, SE Spain): A lately formed Quaternary tectonic feature of the Eastern Betic Shear Zone

The Los Tollos Fault is a recent and important feature of the Eastern Betic Shear Zone, one of the major tectonic structures in South Iberia accommodating the convergence between Nubian and Eurasian plates in the western Mediterranean. The Los Tollos Fault became active by the end of Middle Pleistocene introducing some paleogeographical modifications. Previously mapped as a secondary normal fault related to the Carrascoy Fault, recent research evidences that the Los Tollos Fault is an independent Holocene active left-lateral reverse fault extending for at least 15 km. Data analysis from 4 trenches dug across the fault has revealed the occurrence of at least two paleo-earthquake events during the Holocene. The most recent event is dated between 2,740 and 2,140 yr BP (8th to 2nd centuries BC). The size of the paleoevents is calculated to be Mw 6.3 – 6.6 following empirical regressions on surface rupture length. The recurrence interval is estimated to be between 2,200-6,860 years, fitting a slip rate for the fault between 0.12 and 0.17 mm/yr. Such parameters highlight the Los Tollos Fault as a tectonic structure with a considerable activity located relatively close to densely populated areas. These seismogenic parameters should be considered in future reassessments of the seismic hazard of the region.La falla de Los Tollos es una estructura reciente e importante de la Zona de Cizalla de la Bética Oriental, la principal estructura del sureste de la Península Ibérica que acomoda gran parte de la convergencia entre las placas de Eurasia y Nubia en el Mediterráneo Occidental. La falla de Los Tollos, descrita inicialmente como una falla normal secundaria relacionada con la falla de Carrascoy, comenzó su actividad a finales del Pleistoceno Medio generando algunas modificaciones paleogeográficas significativas. El trabajo que aquí presentamos demuestra su activad durante el Holoceno con una cinemática lateral sinestral con componente inversa a lo largo de una longitud de 15 km, e independiente de la Falla de Carrascoy. Del análisis de los datos obtenidos en 4 trincheras paleosismológicas realizadas a lo largo de la traza de la falla, se han podido interpretar la ocurrencia de al menos 2 paleoterremotos durante el Holoceno, acotándose el evento más reciente entre hace 2.740 y 2.140 años (siglos VIII a II a.C.). La magnitud máxima de estos paleoterremotos, estimada mediante correlaciones empíricas que consideran la longitud de rotura en superficie de la falla, se encuentra entre Mw 6,3 y 6,6, con un periodo de recurrencia comprendido entre 2.200 y 6.860 años. La tasa de deslizamiento neta calculada para la falla se estima entre 0,12 y 0,17 mm/a. Estos parámetros identifican la falla de Los Tollos como una estructura activa situada en las cercanías de áreas densamente pobladas y ponen de manifiesto el interés que tendría considerarla en futuras reevaluaciones de la peligrosidad sísmica en la región

Paleoseismological evidence of holocene activity of the Los Tollos fault (Murcia, se Spain): a lately formed quaternary tectonic feature of the eastern betic shear zone

The Los Tollos Fault is a recent and important feature of the Eastern Betic Shear Zone, one of the major tectonic structures in South Iberia accommodating the convergence between Nubian and Eurasian plates in the western Mediterranean. The Los Tollos Fault became active by the end of Middle Pleistocene introducing some paleogeographical modifications. Previously mapped as a secondary normal fault related to the Carrascoy Fault, recent research evidences that the Los Tollos Fault is an independent Holocene active left-lateral reverse fault extending for at least 15 km. Data analysis from 4 trenches dug across the fault has revealed the occurrence of at least two paleo-earthquake events during the Holocene. The most recent event is dated between 2,740 and 2,140 yr BP (8th to 2nd centuries BC). The size of the paleoevents is calculated to be Mw 6.3 – 6.6 following empirical regressions on surface rupture length. The recurrence interval is estimated to be between 2,200-6,860 years, fitting a slip rate for the fault between 0.12 and 0.17 mm/yr. Such parameters highlight the Los Tollos Fault as a tectonic structure with a considerable activity located relatively close to densely populated areas. These seismogenic parameters should be considered in future reassessments of the seismic hazard of the regionThis work forms part of the research activities carried out in the FASEGEO Project (CGL2009-09726) funded by the Spanish Ministry of Science and Innovatio

An exceptionally long paleoseismic record of a slow-moving fault: the Alhama de Murcia fault (Eastern Betic Shear Zone, Spain)

Most catastrophic earthquakes occur along fast-moving faults, although some of them are triggered by slow-moving ones. Long paleoseismic histories are infrequent in the latter faults. Here, an exceptionally long paleoseismic record (more than 300 k.y.) of a slow-moving structure is presented for the southern tip of the Alhama de Murcia fault (Eastern Betic shear zone), which is characterized by morphological expression of current tectonic activity and by a lack of historical seismicity. At its tip, the fault divides into a splay with two main faults bounding the Góñar fault system. At this area, the condensed sedimentation and the distribution of the deformation in several structures provided us with more opportunities to obtain a complete paleoseismic record than at other segments of the fault. The tectonic deformation of the system was studied by an integrated structural, geomorphological, and paleoseismological approach. Stratigraphic and tectonic features at six paleoseismic trenches indicate that old alluvial units have been repeatedly folded and thrusted over younger ones along the different traces of the structure. The correlation of the event timing inferred for each of these trenches and the application of an improved protocol for the infrared stimulated luminescence (IRSL) dating of K-feldspar allowed us to constrain a paleoseismic record as old as 325 ka. We identifi ed a minimum of six possible paleoearthquakes of Mw = 6-7 and a maximum mean recurrence interval of 29 k.y. This provides compelling evidence for the underestimation of the seismic hazard in the region

First results of paleoseismic recurrence along the El Salvador Fault Zone

La Zona de Falla de El Salvador (ZFES), es una estructura de cizalla con una longitud de al menos 150 km y una dirección de aproximadamente N100ºE. Tanto los estudios morfotectónicos, que muestran desplazamientos en la red fluvial y morfologías típicas de desgarres, como los estudios paleosísmicos indican un movimiento de desgarre dextral con componente extensional para la ZFES. Esta falla afecta materiales volcánicos y aluviales de edad holocena y se encuentra constituida por tres segmentos estructurales principales. De acuerdo con los estudios sismotectónicos previos, el segmento más occidental (Ilopango-San Vicente) fue el responsable del evento sísmico destructivo de Mw 6.6 ocurrido en 2001. La excavación de dos trincheras en este segmento aporta los primeros datos paleosísmicos obtenidos hasta la fecha para esta falla. El estudio preliminar de la estructura de la zona de falla en las trincheras y de la evolución de la deformación paleosísmica mediante la datación de los sedimentos desplazados, nos indica la existencia de al menos tres eventos sísmicos con ruptura superficial en los últimos 1.500 años. La geometría de la fracturación estudiada en la trinchera aporta además valiosos datos para caracterizar la cinemática de la falla, como la dirección y el buzamiento de los planos en la zona de falla o la aparición de estrías, y apoya una tasa de movimiento mínima de 1,9 mm/a.The El Salvador Fault Zone (ESFZ) is a 150 km long, E-W oriented, strike-slip fault and has recently been identified as the source of the destructive Mw 6.6 El Salvador earthquake of 2001. The fault zone comprises three major segments from Lake Ilopango to Golfo de Fonseca. Along this sector the fault displaces recent volcanic and alluvial deposits. According to previous seimotectonic studies, the reactivation of the occidental segment (Ilopango - San Vicente) produced the 2001 damaging seismic event. Holocene activity of this fault segment deforms fluvial terraces and produces morphological features related to strike-slip movement. In this work we present the results of the first paleoseismic analysis carried out on this fault. Trenching studies on the Ilopango-San Vicente segment shows that surface rupture events have occurred at least twice along the fault during the past 1.5 ka. The geometry of faulting exposed in the trench provides valuable insights into the kinematics of the fault, and provides a preliminary minimum net slip rate of 1.9 mm/yr.Depto. de Geodinámica, Estratigrafía y PaleontologíaFac. de Ciencias GeológicasTRUETECSALpu

First month prednisone dose predicts prednisone burden during the following 11 months: An observational study from the RELES cohort

Aim: To study the influence of prednisone dose during the first month after systemic lupus erythematosus (SLE) diagnosis (prednisone-1) on glucocorticoid burden during the subsequent 11 months (prednisone-2–12). Methods: 223 patients from the Registro Español de Lupus Eritematoso Sistémico inception cohort were studied. The cumulative dose of prednisone-1 and prednisone-2–12 were calculated and recoded into a four-level categorical variable: no prednisone, low dose (up to 7.5 mg/day), medium dose (up to 30 mg/day) and high dose (over 30 mg/day). The association between the cumulative prednisone-1 and prednisone-2–12 doses was tested. We analysed whether the four-level prednisone-1 categorical variable was an independent predictor of an average dose >7.5 mg/day of prednisone-2–12. Adjusting variables included age, immunosuppressives, antimalarials, methyl-prednisolone pulses, lupus nephritis and baseline SLE Disease Activity Index (SLEDAI). Results: Within the first month, 113 patients (51%) did not receive any prednisone, 24 patients (11%) received average low doses, 46 patients (21%) received medium doses and 40 patients (18%) received high doses. There was a strong association between prednisone-1 and prednisone-2–12 dose categories (p7.5 mg/day, while patients receiving low-dose prednisone-1 were not (adjusted OR 1.4, 95% CI 0. 0.38 to 5.2). If the analysis was restricted to the 158 patients with a baseline SLEDAI of =6, the model did not change. Conclusion: The dose of prednisone during the first month after the diagnosis of SLE is an independent predictor of prednisone burden during the following 11 months