Local earthquake tomography at the Central Pacific margin off Costa Rica

The Central Pcific area of Costa Rica is a convergent erosional margin, characterized by a high seismicity rate, coincident with the subduction of rough-relief ocean floor. It has generated earthquakes with magnitude up to seven in the past along the subduction megathrust and th inner-forearc faulting. This study uses the records from a temporal seismological network, consisting of on- and offshore stations. Installed for a period of six months in this segment of the Middle American margin. The aim was to obtain a model of the 3-D velocity structure of the margin and to characterize the seismicita of the shallow part (< 70 km depth) of the subduction zone, with the focus on the seismogenic zone. A subset of well locatable events was selected to calculate a minimum 1-D model for the P-wave velocity. This model served as initial reference model for the subsequent 3-D inversion in a Loca Earthquake Tomography, performed by inverting P- and S-wave traveltimes from 595 selected earthquakes. Several tools for resolution assessment were applied. Additionally, first-motion, double-couple focal mechanisms were determined for earthquaeks originated at the plate interface, the subducting slyb and the overriding plate. The results reflect the complexity associated to subduction of ocean-flor morphology and the transition from normal to thickened subducting oceanic crust. The subducting slab ist imaged as a high-velocity perturbation with a conspicuous band of low velocities (LVB) on top, encompassing the intraslab seismicity deeper the ~30 km. The LVB is locally thickened beneath the margin slope by the presence of at least twosubducted seamounts. There is a general eastward widening of the LVB over a relatively short sitance, accentated by a low-velocitiy anomaly beneath the continental shelf, interpreted as a relative big seamount or plateau. The thickening of the subducting crust closely coincides with the onset of an inverted forearc basin onshore and the appearance of an aseismic low-velocity anomaly beneath the inner forearc. The latter is located in a sector where differential uplift of blocks of the subaerial forearc has been described, suggesting tectonic underplating of eroded material against the base of the upper plate crust. Alternatively, the low velocities could be induced by an accumulation of upward migrating fluids. Other observed velocity perturbations are attributed to various proceeses taking place at different depths, such as slab hydration through bend faulting at the trench and outer rise, tectonic erosion and slab dehydration. In the west part of the studied area, the interplate seismicity is clearly distinguished as tightly-packed clustering, dipping ~16-19° between 15 and 25 km depth, beneath the continental shelf. The updip limit of the interplate seismicity closely coincides with temperatures of 150°C and an increase in the P-wave velocities along the blate boundary, and it closely follows the border of the continental shelf. These observations fit within a recently proposed hydrogeological model for erosional margins, which attributes the onset of stick-slip behaviour in the plate interface to a decrease in the abundance of the fluids released by early dehydration reactions in the subducted sediments; escape of overpressured fluids is propitiated by upward percolation through a fractured upper plate. The thickness and mechanical coherence of the upper plate also influence the start of the seismic behavior. Locally, the presence of subducted seamounts and the associated margin disruption updip of the seismogenic zone could shift the onset of seismicity trenchward. As commonly observed in regions with relatively weak plate coupling, higher seismicity rates concur with the presence of seamounts in the seismogenic zone: in this case, the seamount that originated a Mw-7.0 earthquake in 1990 and the above mentioned seamount or plateau revealed by this study. Furthermore, seismic swarms known as “burst”-type were detected by the experiment in these two subareas as well. They are possibly originated by repetitive rupture of the same small relief patches at the seamounts. If interpretation of the anomaly as a big seamount or plateau is correct, it could act as an asperity in the seismogenic zone, able to generate large earthquakes. The downdip limit of the interplate seismicity seems to be thermally controlled, but the available data is not conclusive. In the east part of the studied area, the interplate seismicity becomes scarce and distributes in clusters. Intraslab earthquakes were detected from the outer rise down to depths greater than 100 km. The highest rates coincide with subduction of thickened crust, where they distribute all over the width of the LVB. If slab dehydration enables seismicity, as widely accepted, and hydration of thickened oceanic crust at the outer rise-trench area is much reduced due to impaired bending ability, then hydration at alternative tectonic scenarios seems to play an important role for seismogenesis. The upper plate seismicity is limited trenchward by the margin wedge. Burst-type seismic swarms were also detected in the overriding plate. The focal mechanisms are in good agreement with previous models of upper plate internal deformation. The low-velocity anomaly at the base of the crust in the inner forearc, seems to promote seismicity in its surroundings by high-friction with the overriding plate, and could be linked to a Mw-6.4 earthquake that caused extensive civil damage along the coast in 2004

Gilligan\u27s theory of women\u27s moral development: Implications for student affairs practitioners

More and more educators are beginning to recognize the difference between the moral development of men and women. Rogers (1989) found patterns in recent research that revealed the nontraditional feminine characteristics of care, empowerment, cooperation and emphasis on relationships are starting to be valued, and that there is less emphasis on the traditional male oriented values of competition and independence. Rogers also suggested that the difference between the moral orientation of men and women is a controversial theme that calls for a redefinition of human nature. According to Rogers, in the heart of this redefinition will be a realization of the validity and the worth of the values of the female ethos, which in the Western culture have long been unrecognized and unresearched (p. 1)

Interplate seismicity at the CRISP site: the 2002 Osa earthquake sequence

The Costa Rica Seismogenesis Project (CRISP) is designed to explore the processes involved in the nucleation of large interplate earthquakes in erosional subduction zones. On 16 June 2002 a magnitude Mw=6.4 earthquake and its aftershocks may have nucleated at the subduction thrust to be penetrated and sampled by CRISP, ~40 km west of Osa Peninsula. Global event locations present uncertainties too large to prove that the event actually occurred at a location and depth reachable by riser drilling. We have compiled a database including foreshocks, the main shock, and ~400 aftershocks, with phase arrival times from all the seismological networks that recorded the 2002 Osa sequence locally. This includes a temporal network of ocean-bottom hydrophones (OBH) that happened to be installed close to the area at the time of the earthquake. The coverage increase provided by the OBH network allow us to better constrain the event relocations, and to further analyze the seismicity in the vicinity of Osa for the six months during which they were deployed. Moreover, we undertook teleseismic waveform inversion to provide additional constraints for the centroid depth of the 2002 Osa earthquake, allowing further study of the focal mechanism. Along the Costa Rican seismogenic zone, the 2002 Osa sequence is the most recent. It nucleated in the SE region of the forearc where this erosional margin is underthrust by a seamount covered ocean plate. A Mw=6.9 earthquake sequence occurred in 1999, co-located with a subducted ridge and associated seamounts. The Osa mainshock and first hours of aftershocks began in the CRISP area, ~30 km seaward of the 1999 sequence. In the following two weeks, subsequent aftershocks migrated into the 1999 aftershock area and also clustered in an area updip from it. The Osa updip seismicity apparently occurred where interplate temperatures are ~100°C or less. In this study, we present the relocation of the 2002 Osa earthquake sequence and background seismicity using different techniques and a moment tensor inversion for the mainshock, and discuss the corresponding uncertainties, in an effort to provide further evidence that the planned Phase B of CRISP will be successful in drilling the seismogenic coupling zone

CRISP-EQ: Costa Rican Seismogenic potential outlined by IODP drilling and the 2002 Osa earthquake sequence

Interplate earthquakes in subduction zones are generated in the seismogenic zone, i.e. the segment of the plate boundary where unstable slip occurs. Understanding the mechanisms that control the updip and downdip limits of this zone, as well as the nature and role of asperities within it, provide significant insights into the rupture size and dynamics of the world’s largest earthquakes. The Costa Rica Seismogenesis Project (CRISP) is designed to understand the processes that control nucleation and seismic rupture propagation of large earthquakes at erosive subduction zones (Ranero et al. 2007). In 2002 a magnitude Mw=6.4 earthquake may have nucleated at the subduction thrust to be penetrated and sampled by CRISP, 40 km west of Osa Peninsula (Figure 1). However, global event localization is associated with too large errors to prove that the event actually occurred at a location and depth to be reachable by riser drilling. We have compiled a database including foreshocks, the main shock, and ~400 aftershocks, with readings from all the seismological networks that recorded the 2002 Osa sequence locally (Figure 1). This includes a temporal network of oceanbottom hydrophones (OBH) that happened to be installed close to the area (Arroyo et al. 2009). The greatly improved coverage provided by the OBH enable us to better constrain the event relocations that we are presently undertaking. Within the frame of a proposal recently submitted to DFG with IODP emphasis, detailed inspection of the data and 3-D data modelling will be carried out to yield source parameters that can be rated against structural information from seismic and drilling constraints. Moreover, teleseismic waveform inversion will provide additional constraints for the centroid depth of the 2002 Osa earthquake, allowing further study of the focal mechanism. This sequence is the latest at the Costa Rican seismogenic zone to date, in a segment of the erosional margin where seamount-covered oceanic floor is presently subducting (Figure 1). It took place trenchward from a 1999 Mw=6.9 earthquake sequence, that it is thought to have been nucleated by a seamount acting like an asperity (Bilek et al. 2003). The work proposed here aims to provide definite evidence that the planned Phase B of CRISP will be successful in drilling the seismogenic coupling zone. Furthermore, the seismological data will be interpreted jointly with thermal and drilling data from IODP Expedition 334 to refine the link between temperature and seismogenesis at erosive convergent margins

Factores de riesgo relacionados con la iniciación de la actividad sexual de los adolescentes del Colegio San Agustín. San Isidro. 2019

El objetivo de esta tesis fue determinar la relación entre los factores de riesgo y la iniciación de la actividad sexual de los adolescentes del Colegio San Agustín. San Isidro en el año 2019. La investigación tuvo un enfoque cuantitativo, fue de tipo aplicada de diseño descriptivo, retrospectivo, correlacional de corte transversal. La población estuvo representada por 200 adolescentes y la muestra por 120 adolescentes, se planteó como hipótesis principal que los factores de riesgo se relacionan significativamente con la iniciación de la actividad sexual de los adolescentes. Se empleó como instrumentos fichas de recolección de datos y encuesta validadas por juicios de expertos. Las principales conclusiones fueron que los factores de riesgo se relacionan significativamente con la iniciación de la actividad sexual de los adolescentes; siendo el mayor porcentaje de inicio de relaciones sexuales a la edad de 12 años, en casa, tipo coital, en forma consentida, la mayoría afirma que fue por curiosidad, usó anticonceptivos tipo condón y fue realizado con su enamorado. Los factores de riesgo conductual de deben en un 13.3% al consumo de tabaco y alcohol, el 10% al comportamiento. Los factores de riesgo demográfico de deben en un 5.0% a la edad y el 3.3% al género. Los factores de riesgo medioambiental se deben al 18.3% a los culturales, el 15% a los sociales, el 12.5% a los económicos. Se recomienda realizar un programa de intervención educativa, orientado a la prevención de los factores de riesgo en la iniciación de la actividad sexual de los adolescentes

Intencionalidad y expresión: un análisis de la ausencia en la expresión

"El tema del lenguaje es, por demás, uno de los temas filosóficos por excelencia. De manera tradicional, un estudio filosófico del lenguaje pretende descifrar conceptos como los de significado, sentido, palabra, etc. Es hasta la incursión de Husserl y su fenomenología que un estudio del lenguaje tematiza nociones como las de intencionalidad, vivencia, objeto intencional, etc. Para Husserl, la relevancia de este tratamiento deriva de su crítica del conocimiento y de su pretensión de fundar una lógica pura. Según su convicción, una empresa de tal importancia requiere de la mayor claridad respecto a las proposiciones y significados que manipula. Así, una investigación que pretenda culminar con la construcción de una nueva lógica deberá iniciar con un examen lingüístico"

Sismicidad y ruido sísmico en Costa Rica durante la pandemia del año 2020

Durante el 2020, la Red Sismológica Nacional (RSN) localizó 3480 sismos locales, equivalente a la energía sísmica liberada por un evento de magnitud (Mw) 6,5. La sismicidad se concentró principalmente en seis zonas con 100-350 temblores. Un total de 232 sismos (~7%) fueron sentidos por la población, incluyendo 17 con Mw entre 5,0 y 6,0. La mayoría de los eventos percibidos fueron superficiales (~85% < 30 km) y con Mw baja (~56% < 3,9). Las fallas en las placas cabalgantes provocaron 140 de los sismos sentidos, mientras que la zona sismogénica interplacas de la subducción ocasionó 61, incluyendo el evento más significativo cerca de Jacó en agosto (Mw 6,0). Este sismo y el de Boruca en marzo (Mw 5,6) provocaron las intensidades más altas observadas (VI). Durante el 2020, el nivel de ruido sísmico bajó de 200 a 50 nm debido a las medidas de confinamiento por la pandemia del COVID-19.UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela Centroamericana de Geologí