Evolution of the seismic structure of the incoming/subducting oceanic Nazca Plate off South Central Chile

The release of fluids in subduction zones is believed to be an important process controlling earthquakes both in the downgoing plate and in the seismogenic megathrust fault zone. Depending on the depth of slab dehydration, water may nurture rupture propagation and trigger arc magmatism. Growing number of geophysical evidence suggest that alteration and hydration of the oceanic plate is most vigorous at the trench-outer rise, where extensional bending-related faulting affects the hydrogeology of the oceanic crust and mantle. To better understand the processes of hydration and alteration affecting the oceanic lithosphere prior to and during subduction, I have studied the seismic velocity structure of the oceanic Nazca plate offshore of southern central Chile. A combination of swath bathymetric, wide-angle and reflection seismic data was used to derive 2D velocity-depth models, using joint refraction and reflection travel-time tomography along two main corridors: (i) offshore Isla de Chiloe (~43°S) and (ii) southern Arauco peninsula (~38°S). The study area corresponds to the southern central accretionary Chile margin, where the trench is heavily filled with up to 2.2 km of sediments. The velocity models show P-wave velocities typical for mature fast-spreading crust in the seaward section of the profiles, with uppermost mantle velocities as fast as 8.3-8.4 km/s. Approaching the Chile trench seismic velocities are significantly reduced, however, suggesting that the structure of both the oceanic crust and uppermost mantle have been altered, possibly due to a certain degree of fracturing and hydration. The decrease of the velocities roughly starts at the outer rise; ~100 km from the deformation front, and continues into the trench. Anomalously low heat flow values near outcropping basement highs were founded at the outer rise offshore Isla de Chiloe, suggesting an efficient inflow of cold seawater into the oceanic crust. Hydration and crustal cracks, activated by extensional tectonic stresses, are suggested to govern the reduced velocities in the vicinity of the trench. Considering typical flow distances of 50 km, water might be redistributed over most of the trench-outer rise area. In addition, Poisson's ratios at the lowermost crust and uppermost mantle reach values of ~0.26 and ~0.29, respectively. These features can be explained by an oceanic crust partially weathered, altered and fractured. Relatively high Poisson's ratios in the uppermost mantle may be likely related to partially serpentinized mantle. On the other hand, the comparison of the uppermost mantle P-wave velocities at the crossing point between perpendicular profiles at ~43°S (~90 km seaward from the trench axis) reveals a low degree of Pn anisotropy (<2 %). Offshore southern Arauco peninsula, the Mocha Fracture Zone is obliquely subducting underneath the South American plate and coincides with an area of even slower velocities and thinning of the oceanic crust (10-15 % thinning), suggesting that the incoming fracture zone may enhance the flux of the chemically-bound water into the subduction zone. The low $P_n$ velocities found in the outer rise area span along the subducting plate and reach a maximum depth of 6-8 km in the uppermost mantle, suggesting that as the oceanic plate subducts at the trench, bending and faulting continues to affect the oceanic lithosphere. The restoring to 'normal' mantle velocities of ~8.4 km/s coincide with the 400-430°C isotherm. This depth is interpreted as the depth limit of hydro-alteration within the upper part of the oceanic lithosphere, where extensional stresses dominate

Outer rise seismicity related to the Maule, Chile 2010 mega-thrust earthquake and hydration of the incoming oceanic lithosphere

Most of the recent published geodetic models of the 2010 Maule, Chile mega-thrust earthquake (Mw=8.8) show a pronounced slip maximum of 15-20 m offshore Iloca (similar to 35 degrees S), indicating that co-seismic slip was largest north of the epicenter of the earthquake rupture area. A secondary slip maximum 8-10 m appears south of the epicenter west of the Arauco Peninsula. During the first weeks following the main shock and seaward of the main slip maximum, an outer rise seismic cluster of >450 events, mainly extensional, with magnitudes Mw=4-6 was formed. In contrast, the outer rise located seaward of the secondary slip maximum presents little seismicity. This observation suggests that outer rise seismicity following the Maule earthquake is strongly correlated with the heterogeneous coseismic slip distribution of the main megathrust event. In particular, the formation of the outer-rise seismic cluster in the north, which spatially correlates with the main maximum slip, is likely linked to strong extensional stresses transfered from the large slip of the subducting oceanic plate. In addition, high resolution bathymetric data reveals that bending-related faulting is more intense seaward of the main maximum slip, where well developed extensional faults strike parallel to the trench axis. Also published seismic constraints reveal reduced P-wave velocities in the uppermost mantle at the trench-outer rise region (7.5-7.8 km/s), which suggest serpentinization of the uppermost mantle. Seawater percolation up to mantle depths is likely driven by bending related-faulting at the outer rise. Water percolation into the upper mantle is expected to be more efficient during the co-seismic and early post-seismic periods of large megathrust earthquakes when intense extensional faulting of the oceanic lithospher

Evaluacion de la captura de insectos no blanco en nuevos disenos y cebos de trampas para adultos de la polilla de la manzana (Cydia pomonella) en un huerto de manzana de la region del Maule

29 p.El uso de distintas trampas y cebos para el monitoreo de la polilla de la manzana (Cydia pomonella) ha evolucionando durante estos últimos años, con los cuales se busca lograr atraer tanto machos como hembras. Uno de los nuevos cebos utilizados es el éster de pera en conjunto con ácido acético; además el éster de pera en combinación con feromonas sexuales, con los cuales se ha permitido obtener buenos resultados en la captura de machos y hembras. Sin embargo una de las problemáticas de estas nuevas trampas son los insectos no blanco que estos cebos pueden capturar, ya que existen diversos reportes de insectos no blanco capturados por estas trampas y cebos. Debido a esto se dispuso en el huerto las cinco configuraciones cebo-trampa (Trampas blancas cebadas con feromona sexual, trampas blancas cebadas con feromona sexual y éster de pera, trampas naranjas cebadas con feromona sexual y éster de pera trampas delta transparente cebada con éster de pera y ácido acético y trampas cilíndricas transparente cebadas con éster de pera y ácido acético) en un huerto de manzana abandonado, donde se evaluaron las capturas de insectos no blanco, durante la temporada 2009-2010. Dándonos como resultado que el color de las trampas es más importante que los cebos utilizados para la captura de insectos no blanco. Las trampas de color blanco, cebadas con feromona sexual sola y cebadas con éster de pera y feromona sexual en conjunto,capturaron un mayor número de himenópteros. Por el contrario, las trampas transparentes capturaron significativamente más hemípteros y dípteros lo que nos podría indicar que el ácido acético podría influenciar la captura de esos insectos. La trampa naranja capturó niveles bajos de himenópteros y dípteros, e intermedios de hemípteros por lo que desde el punto de vista de la captura de insectos no blanco sería la más recomendable para el monitoreo de Cydia pomonella./ ABSTRACT:The use of different traps and lures to attract males and females of the codling moth (Cydia pomonella) has changed in the last years. Some of the new baits used are pear ester with the sexual pheromone (codlemone) and the incorporation of acetic acid in orange and transparent delta traps, which have shown good results in the capture of males and females. However, one problem of these new traps and lures is the capture of non-target insects. In this work new trap designs and lures were evaluated to evaluate the capture of non-target insects in an abandoned apple orchard at Escuela Agrícola de Colín (Talca, Región del Maule), during the 2009-2010 season. The following traps and lures were used: i) transparent delta trap with pear ester and acetic acid, ii) transparent round trap with pear ester and acetic acid, iii) white delta trap with codlemone, iv) white delta trap with codlemone and pear ester, and v) orange delta trap with codlemone and pear ester. Non-target insect capture was more affected by trap color than by lures. White traps, either with codlemone or with pear ester and codlemone, captured a higher number of Hymenoptera. On the contrary, transparent traps with pear ester and acetic acid captured significantly more Hemiptera and Diptera. Orange delta traps with pear ester and codlemone captured few Hymenoptera and Diptera, and intermediate levels of Hemiptera. Therefore, form the point of view of reduced catches of non-target insects the orange delta trap with pear ester and codlemone is more suitable for Cydia pomonella monitoring

Mfd Protects Against Oxidative Stress in Bacillus Subtilis Independently of its Canonical Function in DNA Repair

Background: Previous reports showed that mutagenesis in nutrient-limiting conditions is dependent on Mfd in Bacillus subtilis. Mfd initiates one type of transcription-coupled repair (TCR); this type of repair is known to target bulky lesions, like those associated with UV exposure. Interestingly, the roles of Mfd in repair of oxidative-promoted DNA damage and regulation of transcription differ. Here, we used a genetic approach to test whether Mfd protected B. subtilis from exposure to two different oxidants. Results: Wild-type cells survived tert-butyl hydroperoxide (t-BHP) exposure significantly better than Mfd-deficient cells. This protective effect was independent of UvrA, a component of the canonical TCR/nucleotide excision repair (NER) pathway. Further, our results suggest that Mfd and MutY, a DNA glycosylase that processes 8-oxoG DNA mismatches, work together to protect cells from lesions generated by oxidative damage. We also tested the role of Mfd in mutagenesis in starved cells exposed to t-BHP. In conditions of oxidative stress, Mfd and MutY may work together in the formation of mutations. Unexpectedly, Mfd increased survival when cells were exposed to the protein oxidant diamide. Under this type of oxidative stress, cells survival was not affected by MutY or UvrA. Conclusions: These results are significant because they show that Mfd mediates error-prone repair of DNA and protects cells against oxidation of proteins by affecting gene expression; Mfd deficiency resulted in increased gene expression of the OhrR repressor which controls the cellular response to organic peroxide exposure. These observations point to Mfd functioning beyond a DNA repair factor in cells experiencing oxidative stress

Alteration of the subducting oceanic lithosphere at the southern central Chile trench-outer rise

Hydrothermal circulation and brittle faulting processes affecting the oceanic lithosphere are usually confined to the upper crust for oceanic lithosphere created at intermediate to fast spreading rates. Lower crust and mantle rocks are therefore relatively dry and undeformed. However, recent studies at subduction zones suggest that hydration of the oceanic plate is most vigorous at the trench–outer rise, where extensional bending-related faulting affects the hydrogeology of the oceanic crust and mantle. To understand the degree of hydration, we studied the seismic velocity structure of the incoming Nazca plate offshore of southern central Chile (∼43°S); here the deep-sea trench is heavily filled with up to 2 km of sediments. Seismic refraction and wide-angle data, complemented by seismic reflection imaging of sediments, are used to derive a two-dimensional velocity model using joint refraction and reflection traveltime tomography. The seismic profile runs perpendicular to the spreading ridge and trench axes. The velocity model derived from the tomography inversion consists of a ∼5.3-km-thick oceanic crust and shows P wave velocities typical for mature fast spreading crust in the seaward section of the profile, with uppermost mantle velocities as fast as ∼8.3 km/s. Approaching the Chile trench, seismic velocities are significantly reduced, however, suggesting that the structures of both the oceanic crust and uppermost mantle have been altered, possibly due to a certain degree of fracturing and hydration. The decrease of the velocities roughly starts at the outer rise, ∼120 km from the deformation front, and continues into the trench. Even though the trench is filled with sediment, basement outcrops in the outer rise frequently pierce the sedimentary blanket. Anomalously low heat flow values near outcropping basement highs indicate an efficient inflow of cold seawater into the oceanic crust. Hydration and crustal cracks activated by extensional bending-related faulting are suggested to govern the reduced velocities in the vicinity of the trench. Considering typical flow distances of 50 km, water might be redistributed over most of the trench–outer rise area. Where trapped in faults, seawater may migrate down to mantle depth, causing up to ∼9% of serpentinization in at least the uppermost ∼2 km of the mantle between the outer rise and the trench axis

Resistencia a insecticidas en poblaciones de Cydia pomonella L. y Myzus persicae nicotianae

48 p. Incluye 2 resumenesLa polilla de la manzana (Cydia pomonella L.) es la principal plaga de pomáceas y nogales en Chile, siendo controlada casi exclusivamente con aplicaciones de insecticidas órgano fosforados. Sin embargo, durante las ultimas temporadas se han observado crecientes niveles de frutos dañados a cosecha. Es sabido que esta plaga ha desarrollado resistencia a insecticidas en varios países, por lo cual se evaluó resistencia a insecticidas y actividad de enzimas detoxificadoras en muestras colectadas en tres huertos de manzano de la Región del Maule (34° 53' - 35° 29' S) y en una cepa susceptible de referencia mantenida en laboratorio por varios años. Se colectaron larvas en diapausa mediante trampas de cartón corrugado, para evaluar dosis diagnostico de azinfosmetil (organofosforado) y tebufenozide (diacilhidrazina). La actividad de enzimas detoxificadoras fue determinada en los adultos obtenidos de las larvas en diapausa colectadas. La actividad de oxidasas de función múltiple (MFO) y glutation-S-transferasas (GST) fue medida a través de fluorimetria, mientras la de esterasas (EST) fue determinada por absorbancia. La mortalidad larval para azinfosmetil fue significativamente menor para Molina (30%) y Teno (85,4%) que para la cepa de referencia de laboratorio (95,3%). Para tebufenozide la mortalidad larval fue significativamente menor en Molina (35,31%) que en la cepa de referencia (88,6%). En los huertos de Teno (13.679,4 unidades de fluorescencia insecto-) y Molina (13.096,1 unidades de fluorescencia insect()-) se observo una actividad de GST significativamente mayor. De igual forma, la actividad de MFO fue significativamente mds alta en los mismos huertos con valores de mayor 25,08 y 17,95 pg de 7OH insecto 'minuto' para Molina y Teno respectivamente. Finalmente, no hubo diferencias significativas en la actividad de EST de las distintas muestras

Efecto de dos extractos alcoholicos de Azadirachta indica Juss sobre el desarrollo de mosaico del pepino en plantas de pimenton

Resumen (Spanish, English)43 p.Se realizó un experimento bajo condiciones de invernadero para determinar el efecto de dos extractos alcohólicos de Neem (Bionim y Neem-X) a una concentración de 45 ppm de azadirachtina, sobre el desarrollo del Mosaico del Pepino en plantas de pimentón (Capsicum annuum var. grossum), inoculadas mecánicamente. Se evaluaron aplicaciones previas y posteriores a la infección de las plantas con CMV, determinándose la incidencia y presencia de virus transcurridos 10, 20 y 30 días desde la inoculación. Ninguno de los productos pareció tener efecto en la expresión de síntomas; pero ambos extractos, independiente del momento de aplicación, fueron capaces de afectar la presencia del virus, de acuerdo a la prueba serológica DAS-ELISA; presentándose claras diferencias entre los tratamientos y los controles enfermos, siendo los valores obtenidos muy similares a los controles sanos

Tectonic control on sediment accretion and subduction off south central Chile: Implications for coseismic rupture processes of the 1960 and 2010 megathrust earthquakes

Based on a compilation of published and new seismic refraction and multichannel seismic reflection data along the south central Chile margin (33°–46°S), we study the processes of sediment accretion and subduction and their implications on megathrust seismicity. In terms of the frontal accretionary prism (FAP) size, the marine south central Chile fore arc can be divided in two main segments: (1) the Maule segment (south of the Juan Fernández Ridge and north of the Mocha block) characterized by a relative large FAP (20–40 km wide) and (2) the Chiloé segment (south of the Mocha block and north of the Nazca-Antarctic-South America plates junction) characterized by a small FAP (≤10 km wide). In addition, the Maule and Chiloé segments correlate with a thin (<1 km thick) and thick (∼1.5 km thick) subduction channel, respectively. The Mocha block lies between ∼37.5° and 40°S and is configured by the Chile trench, Mocha and Valdivia fracture zones. This region separates young (0–25 Ma) oceanic lithosphere in the south from old (30–35 Ma) oceanic lithosphere in the north, and it represents a fundamental tectonic boundary separating two different styles of sediment accretion and subduction, respectively. A process responsible for this segmentation could be related to differences in initial angles of subduction which in turn depend on the amplitude of the down-deflected oceanic lithosphere under trench sediment loading. On the other hand, a small FAP along the Chiloé segment is coincident with the rupture area of the trans-Pacific tsunamigenic 1960 earthquake (Mw = 9.5), while a relatively large FAP along the Maule segment is coincident with the rupture area of the 2010 earthquake (Mw = 8.8). Differences in earthquake and tsunami magnitudes between these events can be explained in terms of the FAP size along the Chiloé and Maule segments that control the location of the updip limit of the seismogenic zone. The rupture area of the 1960 event also correlates with a thick subduction channel (Chiloé segment) that may provide enough smoothness at the subduction interface allowing long lateral earthquake rupture propagation

Reloca Slide: an ~24 km³ submarine mass wasting event in response to over-steepening and failure of the central Chilean continental slope

Reloca Slide is the relict of an ~24 km³ submarine slope collapse at the base of the convergent continental margin of central Chile. Bathymetric and seismic data show that directly to the north and south of the slide the lower continental slope is steep (~10°), the deformation front is shifted landwards by 10–15 km, and the frontal accretionary prism is uplifted. In contrast, ~80 km to the north the lower continental margin presents a lower slope angle of about 4° and a wide frontal accretionary prism. We propose that high effective basal friction conditions at the base of the accretionary prism favored basal accretion of sediment and over-steepening of the continental slope, producing massive submarine mass wasting in the Reloca region. This area also spatially correlates with a zone of low coseismic slip of the 2010 Maule megathrust earthquake, which is consistent with high basal frictional coefficients