An improved input energy spectrum verified by the shake table tests

Input energy is the principal component of the energy balance equation. It is beneficial to determine, through its components, how the recoverable and irrecoverable energies are distributed within the structural elements. Several equations and attenuation relations to define mass-normalized input energy spectra exist in the literature. They are mainly proposed for elastic systems subjected to far-fault EQs. There is a lack of experimental verification of these proposed spectra. In this paper, experimental assessment was performed to the existing spectra, and further improvements were accomplished. For this purpose, steel cantilever columns were tested on the shake table for two specific historical EQs coincidently having similar spectral acceleration values. Based on the experimental results, a three-part mass-normalized relative input energy spectrum was formulated including soil type, EQ (corner period, intensity, duration, spectral acceleration, and velocity), and structural behavioral characteristics (period and structural damping). The proposed input energy spectrum was experimentally calibrated and numerically validated for various EQs featuring near- and far-field types. Analytical and experimental comparisons were made between the previously developed spectrum and the newly proposed one. The validation studies and the statistical evaluations exposed that the proposed spectrum yielded better agreement with the experimental and numerical results.     

Hamilton Harbour, Ontario: 8300 years of limnological and environmental change inferred from microfossil and isotopic analyses

Limnological changes in Hamilton Harbour, Lake Ontario, over the Holocene were investigated by using proxy evidence from diatoms and other siliceous microfossils in a radiometrically dated sediment core (HH26comp), together with environmental data derived from sediment pollen and oxygen and carbon isotope analyses. The evidence demonstrates that the site of Hamilton Harbour has changed over the past 8300 y from a shallow, separate waterbody, to a deep embayment of Lake Ontario. The earliest evidence, from 8300 BP to 7000 BP, is of a mesotrophic pond of moderate alkalinity, warmer than present, and probably with an extensive marginal wetland. An initial transitory connection with the rising water level of Lake Ontario was established at c. 7000 BP, possibly via a deep outlet channel. This connection is 2000 y earlier then previously estimated. Permanent confluence with Lake Ontario was established at c. 6200 BP, causing a decline in inferred trophic level and water temperatures. Microfossils reach a minimum at 4400 BP coincident with the Nipissing Flood. Decreased mixing of Lake Ontario water from about 4000 BP following the Nipissing Flood highstand is evidenced in isotopic and diatom data. Three isolated shifts in the diatom spectrum at c. 4900 BP, 4500 BP, and 3500 BP may be associated with extreme turbidity or storm deposit events. Between 3200 BP and 280 BP, Hamilton Harbour was evidently a moderately alkaline embayment of Lake Ontario, oligotrophic to mesotrophic, and relatively cooler than present. The final 280 y sedimentary record reveals the magnitude of anthropogenically induced changes to the harbour, including eutrophication and organic pollution.     

Using a Thermal Proxy to Examine Sediment–Water Exchange in Mid-Continental Shelf Sandy Sediments

Fluid exchange across the sediment–water interface in a sandy open continental shelf setting was studied using heat as a tracer. Summertime tidal oscillation of cross-shelf thermal fronts on the South Atlantic Bight provided a sufficient signal at the sediment–water interface to trace the advective and conductive transport of heat into and out of the seabed, indicating rapid flushing of ocean water through the upper 10–40 cm of the sandy seafloor. A newly developed transport model was applied to the in situ temperature data set to estimate the extent to which heat was transported by advection rather than conduction. Heat transported by shallow 3-D porewater flow processes was accounted for in the model by using a dispersion term, the depth and intensity of which reflected the depth and intensity of shallow flushing. Similar to the results of past studies in shallower and more energetic nearshore settings, transport of heat was greater when higher near-bed velocities and shear stresses occurred over a rippled bed. However, boundary layer processes by themselves were insufficient to promote non-conductive heat transport. Advective heat transport only occurred when both larger boundary layer stresses and thermal instabilities within the porespace were present. The latter process is dependent on shelf-scale heating and cooling of bottom water associated with upwelling events that are not coupled to local-scale boundary layer processes.     

Zero-offset P–S energy in horizontally layered media

The existence of non‐zero reflectivity for zero‐offset PS waves in horizontally layered media is discussed. Field measurements have suggested the occurrence of this phenomenon. We show that, in some cases, if anisotropy is considered in the problem, this reflectivity can be predicted. By using an approximated formulation to determine the coefficient of reflection in arbitrarily anisotropic media, it is clear that, for some elastic arrangements of the subsurface, reflected energy is associated with the converted wave resulting from normal P‐wave incidence.     

CU Eridani — A suspected variable

Photometric observations of CU Eridani, recently classified as non-variable, indicate it to be a variable star.     

Morphostratigraphy and fan morphology of doon valley

In the present study analysis of Landsat MSS, TM and SPOT imagery and digital analysis of IRS LISS-1 data of Doon Valley was carried out. Various geomorphic features were identified and classified, morphostratigraphy of the area has been established. Main geomorphic units of the area are Mussoorie Hill Range (Denudational), Siwalik Hills (Structural), Remnant Hills (Residual). Siwalik Piedmont. Doon Piedmont, River Terraces and Flood Plain. Three large fan lobes are identified on Doon Piedmont deposits, viz., Western fan lobe, Central fan lobe and Eastern fan lobe. Average slope of these three fan lobes are 2°21′, 2°3′, and 1°24′ for the western, central and eastern fan lobes respectively. Western and central fan lobes have been affected by neotectonic activity which is reflected in transverse profiles.     

An automatic system for continuous monitoring of CO2, H2S, SO2 and meteorological parameters in the atmosphere of volcanic areas

An automatic system for the continuous monitoring of CO₂, H₂S, SO₂ and meteorological parameters in atmosphere has been developed. The system has been tested in the laboratory in order to verify the stability and reliability of each sensor and of the whole system. A field test for a period of one month, at the Solfatara of Pozzuoli has also been carried out. The acquired data during the field test reveal a correlation between the wind speed and the concentrations of CO₂, H₂S, and SO₂ in the atmosphere. With a wind speed of over 4 ms^-1 the concentration of the three gases reached constant background values of 600 ppm for CO₂ and about 2 ppm vol. for H₂S and SO₂. The different ratios of H₂S/SO₂ measured in the fumaroles (~100) and in the atmosphere (1–0.1) clearly indicate that H₂S is oxidized to SO₂ during the transport.