Source history of the 1905 great Mongolian earthquakes (Tsetserleg, Bolnay)   总被引：1，自引：0，他引：1  

Antoine Schlupp  Armando Cisternas 《Geophysical Journal International》2007,169(3):1115-1131

Two great Mongolian earthquakes, Tsetserleg and Bolnay, occurred on 1905 July 9 and 23. We determined the source history of these events using body waveform inversion. The Tsetserleg rupture (azimuth N60°) correspond to a N60° oriented branch of the long EW oriented Bolnay fault.
Historical seismograms recorded by Wiechert instruments are digitized and corrected for the geometrical deformation due to the recording system. We use predictive filters to recover the signals lost at the minute marks.
The total rupture length for the Tsetserleg earthquake may reach up to 190 km, in order to explain the width of the recorded body waves. This implies adding 60 km to the previously mapped fault. The rupture propagation is mainly eastward. It starts at the southwest of the central subsegment, showing a left lateral strike-slip with a reverse component. The total duration of the modelled source function is 65 s. The seismic moment deduced from the inversion is 10²¹ N m, giving a magnitude   M _w = 8  .
The nucleation of the Bolnay earthquake was at the intersection between the main fault (375 km left lateral strike-slip) and the Teregtiin fault (N160°, 80 km long right lateral strike-slip with a vertical component near the main fault). The rupture was bilateral along the main fault: 100 km to the west and 275 km to east. It also propagated 80 km to the southeast along the Teregtiin fault. The source duration was 115 s. The moment magnitude Mw varies between 8.3 and 8.5.
The nucleation and rupture depths remain uncertain. We tested three cases: (1) nucleation and rupture depth limited to the seismogenic zone; (2) nucleation in the seismogenic zone and rupture propagation going to the base of the crust and (3) nucleation within the crust–upper mantle interface and rupture propagation within the upper mantle.  相似文献   

Semi‐empirical model for site effects on acceleration time histories at soft‐soil sites. Part 2: calibration     

Armando Brcena  Luis Esteva 《地震工程与结构动力学》2004,33(13):1287-1310

A previously developed simplified model of ground motion amplification is applied to the simulation of acceleration time histories at several soft‐soil sites in the Valley of Mexico, on the basis of the corresponding records on firm ground. The main objective is to assess the ability of the model to reproduce characteristics such as effective duration, frequency content and instantaneous intensity. The model is based on the identification of a number of parameters that characterize the complex firm‐ground to soft‐soil transfer function, and on the adjustment of these parameters in order to account for non‐linear soil behavior. Once the adjusted model parameters are introduced, the statistical properties of the simulated and the recorded ground motions agree reasonably well. For the sites and for the seismic events considered in this study, it is concluded that non‐linear soil behavior may have a significant effect on the amplification of ground motion. The non‐linear soil behavior significantly affects the effective ground motion duration for the components with the higher intensities, but it does not have any noticeable influence on the lengthening of the dominant ground period. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Relatively short-term correlation among deformation,degassing, and seismicity: a case study from Concepción volcano,Nicaragua   总被引：1，自引：0，他引：1  

José Armando Saballos  Vladimir Conde  Rocco Malservisi  Charles B. Connor  Julio Álvarez  Angélica Muñoz 《Bulletin of Volcanology》2014,76(8):1-11

Concepción is a frequently active composite volcano in Nicaragua, and is located on Ometepe Island, within Lake Nicaragua. Significant eruptive activity took place at this volcano between March and May 2010, consisting of ash and gas explosions (VEI 1–2). We compare geodetic baseline changes observed with global positioning system (GPS), sulfur dioxide flux (SO₂), and seismic amplitude (SAM) data collected at Concepción during April – June, 2010, and February – April, 2011. Time series analysis reveals a remarkable correlation among the data sets during 2010, when the volcano was erupting. In contrast, the volcano was at its background level of activity in 2011 and the statistical correlation among the time series is not significant for this period. We explain the emergence of correlation among the time series during eruptive activity through modeling of the GPS data with emplacement of a magma column in an open conduit. In the model, magma rose in the conduit, between May 5 and 14, 2010, from a shallow reservoir located at ～ 1.8 km depth. Later, between May 24 and 31, 2010, the top of the magma column descended to almost 600 m depth, corresponding to the cessation of eruptive activity. Thus, cross-correlation and an integrated analysis of these geophysical time series on a timescale of days helps to reveal the dynamics of the magma plumbing system operating below Concepción volcano.  相似文献   

Infrared (0.83-5.1 μm) photometry of Phoebe from the Cassini Visual Infrared Mapping Spectrometer     

B.J. Buratti  K. Soderlund  J.A. Mosher  D.P. Simonelli  R.N. Clark  D.P. Cruikshank 《Icarus》2008,193(2):309-322

Three weeks prior to the commencement of Cassini's 4 year tour of the saturnian system, the spacecraft executed a close flyby of the outer satellite Phoebe. The infrared channel of the Visual Infrared Mapping Spectrometer (VIMS) obtained images of reflected light over the 0.83-5.1 μm spectral range with an average spectral resolution of 16.5 nm, spatial resolution up to 2 km, and over a range of solar phase angles not observed before. These images have been analyzed to derive fundamental photometric parameters including the phase curve and phase integral, spectral geometric albedo, bolometric Bond albedo, and the single scattering albedo. Physical properties of the surface, including macroscopic roughness and the single particle phase function, have also been characterized. Maps of normal reflectance show the existence of two major albedo regimes in the infrared, with gradations between the two regimes and much terrain with substantially higher albedos. The phase integral of Phoebe is 0.29±0.03, with no significant wavelength dependence. The bolometric Bond albedo is 0.023±007. We find that the surface of Phoebe is rough, with a mean slope angle of 33°. The satellite's surface has a substantial forward scattering component, suggesting that its surface is dusty, perhaps from a history of outgassing. The spectrum of Phoebe is best matched by a composition including water ice, amorphous carbon, iron-bearing minerals, carbon dioxide, and Triton tholin. The characteristics of Phoebe suggest that it originated outside the saturnian system, perhaps in the Kuiper Belt, and was captured on its journey inward, as suggested by Johnson and Lunine (2005).  相似文献   

Water column characterisation on the Azores platform and at the sea mounts south of the archipelago     

C Palma  AI Lillebø  C Borges  M Souto  E Pereira  AC Duarte  MP Abreu 《Marine pollution bulletin》2012,64(9):1884-1894

This study provides data concerning the hydrography and water chemistry of the Atlantic region between 29-38° N and 27-31° W, and establishes background values for dissolved Cu, Cd, Pb and As. Three water masses were identified: the Eastern North Atlantic Central Water (ENACW), the Mediterranean Water (MW) and the North Atlantic Deep Water (NADW). The ENACW exhibits a clear meridional gradient of temperature and salinity, with comparatively high values at the southern sites and lower values on the Azores platform. The ENACW, which includes the euphotic zone, also had comparatively high concentrations of oxygen and lower concentrations of nutrients and metals. The Cu, Cd and Pb results suggest that new background concentrations for OSPAR Region V (the Wider Atlantic) should be established as follows: 0.15-13nM for Cu, 0.05-1.4nM for Cd and 0.03-5nM for Pb. The background concentrations of As for OSPAR Region V should be 7-28nM.  相似文献   

Evaluation of pseudostatic active earth pressure coefficient of cantilever retaining walls     

Aldo Evangelista  Anna Scotto di Santolo  Armando Lucio Simonelli 《Soil Dynamics and Earthquake Engineering》2010

A stress plasticity solution is proposed for evaluating the gravitational and dynamic active earth pressures on cantilever retaining walls with long heel. The solution takes into account the friction angle of the soil, wall roughness, backfill inclination and horizontal and vertical seismic accelerations. It is validated by means of the comparison with both traditional limit equilibrium methods (e.g. Mononobe–Okabe equations) and static and pseudostatic numerical FLAC analyses. For numerical analyses the soil is modelled as an elasto-plastic non-dilatant medium obeying the Mohr–Coulomb yield criterion, while the wall is elastic. The solutions for the horizontal and vertical seismic coefficients are proposed, which allow one to determine the intensity of the active thrust and its inclination δ with respect to the horizontal. It is demonstrated that the latter also depends on the soil friction angle φ. The inclination in seismic conditions δ_E is greater than the one in static conditions, δ_S, usually adopted in both cases. As a matter of fact, since wall stability conditions improve with the increase of inclination δ, the present method gives solutions that are less onerous than traditional ones, producing less conservative wall designs. Finally pseudostatic results are compared with proper dynamic analyses (by FLAC code) performed utilising four Italian accelerometric time-histories as input ground motion.  相似文献   

Air–Water CO<Subscript>2</Subscript> Fluxes and Net Ecosystem Production Changes in a Baja California Coastal Lagoon During the Anomalous North Pacific Warm Condition     

Ma Carmen Ávila-López  J. Martín Hernández-Ayón  Víctor F. Camacho-Ibar  Armando Félix Bermúdez  Adan Mejía-Trejo  Isaí Pacheco-Ruiz  Jose M. Sandoval-Gil 《Estuaries and Coasts》2017,40(3):792-806

The present study examines the temporal variability of air–water CO₂ fluxes (FCO₂) and seawater carbonate chemistry in a Baja California coastal lagoon during an exceptionally warm anomaly that was developed in Northeast Pacific coasts during 2014. This oceanographic condition led to a summer-like season (weak upwelling condition) during the study period, which reached a maximum surface temperature anomaly of 2 °C in September 2014. San Quintín Bay acts as a source of CO₂ to the atmosphere in 2014 (3.3 ± 4.8 mmol C m^?2 day^?1) with the higher positive fluxes mainly observed in summer months (9.0 ± 5.3 mmol C m^?2 day^?1). Net ecosystem production (NEP) switched seasonally between net heterotrophy and net autotrophy during the study period, with an annual average of 2.2 ± 7.1 mmol C m^?2 day^?1, which indicates that San Quintín Bay was a net autotrophic system during the atypical warm oceanographic condition in 2014. This pattern of seasonal variations in the carbon balance at San Quintín Bay appears to be linked to the life cycle of benthic communities, which play an important role in the whole-ecosystem metabolism. Under the limited input from external sources coupled with an increase in seawater temperatures, the recycled benthic carbon and nutrient fluxes play a major role to sustain water-column processes within the bay. Since the upwelling condition may influence the magnitude of the air–water CO₂ fluxes, our results clearly indicated that San Quintín Bay is a net source of carbon to the atmosphere regardless of the adjacent oceanic conditions. Our study sheds light on the carbon dynamics and its metabolic implications in a shallow coastal ecosystem under a regional warm anomaly and contributes potentially relevant information in view of the likely future scenario of global climate change.  相似文献   

A Study of the Solar-Like Properties of β Hydri     

Maria Pia Di Mauro  Jørgen Christensen-Dalsgaard  Lucio Paternò 《Astrophysics and Space Science》2003,284(1):229-232

We investigate properties of the internal structure of HR2021, better known as Hydri, a G2 IV subgiant with mass close to solar and for which observations by Bedding et al. (2001) have shown the presence of solar-like oscillations.We have computed models of Hydri,based on updated global parameters,and compared the computed frequencies for the models with the observed oscillation spectrum.  相似文献   

Evidence of oil leakage from the Bahía Paraíso wreck in Arthur Harbour, Antarctica     

Janiot LJ  Sericano JL  Marcucci O 《Marine pollution bulletin》2003,46(12):1619-1622

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Toxicity of 1,4-dichlorobenzene in sediments to juvenile polychaete worms   总被引：1，自引：0，他引：1  

McPherson CA  Tang A  Chapman PM  Taylor LA  Gormican SJ 《Marine pollution bulletin》2002,44(12):1405-1414

Investigation of sediment contamination associated with a marine sewage outfall in Victoria (BC, Canada) found elevated concentrations of 1,4-dichlorobenzene (1,4-DCB). Juvenile polychaete worm (Neanthes) growth was significantly reduced at or near the outfall, roughly corresponding to elevated 1,4-DCB concentrations. There are few data on 1,4-DCB toxicity to marine organisms and no published literature on its toxicity to benthic marine organisms. To determine whether reduced polychaete growth (measured as dry weight) was due to 1,4-DCB exposure, a laboratory investigation was conducted. Uncontaminated marine sediment was spiked with 1,4-DCB and juvenile Neanthes were exposed in 20-d sublethal toxicity tests. There were no adverse effects on survival at any test concentration; mean survival was 80–100%. Statistically significant decreases in average dry weight only occurred at the highest 1,4-DCB concentration (19,900 μg/kg, dry weight); this represented a 1,4-DCB concentration more than 10 times higher than previously measured at the outfall (1710 μg/kg, dry weight). There were no adverse effects on survival or dry weight at the range of concentrations previously measured in sediments from the vicinity of the outfall.  相似文献