Impacts of simulated M9 Cascadia Subduction Zone earthquakes considering amplifications due to the Georgia sedimentary basin on reinforced concrete shear wall buildings

Southwest British Columbia has the potential to experience large‐magnitude earthquakes generated by the Cascadia Subduction Zone (CSZ). Buildings in Metro Vancouver are particularly vulnerable to these earthquakes because the region lies above the Georgia sedimentary basin, which can amplify the intensity of ground motions, particularly at medium‐to‐long periods. Earthquake design provisions in Canada neglect basin amplification and the consequences of accounting for these effects are uncertain. By leveraging a suite of physics‐based simulations of M9 CSZ earthquakes, we develop site‐specific and period‐dependent spectral acceleration basin amplification factors throughout Metro Vancouver. The M9 simulations, which explicitly account for basin amplification for periods greater than 1s, are benchmarked against the 2016 BC Hydro ground motion model (GMM), which neglects such effects. Outside the basin, empirical and simulated seismic hazard estimates are consistent. However, for sites within the basin and periods in the 1‐5 s range, GMMs significantly underestimate the hazard. The proposed basin amplification factors vary as a function of basin depth, reaching a geometric mean value as high as 4.5 at a 2‐s period, with respect to a reference site located just outside the basin. We evaluate the impact of the M9 simulations on tall reinforced concrete shear wall buildings, which are predominant in the region, by developing a suite of idealized structural systems that capture the strength and ductility intended by historical seismic design provisions in Canada. Ductility demands and collapse risk conditioned on the occurrence of the M9 simulations were found to exceed those associated with ground motion shaking intensities corresponding to the 975 and 2475‐year return periods, far exceeding the ～500‐year return period of M9 CSZ earthquakes.     

Visible continuum emission and gravity waves

Observed oscillations in the visible continuum emission (5000 Å) are studied considering the usual visible emission mechanism, NO + O (both two-body and three-body paths). Characteristic parameters of internal gravity waves are obtained using Hines' linear theory. Values of the kinetic energy density ?, and temperature variations Δθ, due to gravity waves are calculated. The results (? ~ 10⁶cm²s^?2, Δθ = 4–9K) are in agreement with those obtained by means of different techniques reported in the literature. A similar analysis of the simultaneous green-line emission data is made and a comparison is drawn between the results obtained for both emissions. An expression relating relative brightness of continuum emission and relative perturbations of atmospheric density is proposed.     

A regional approach to cultural preservation: A central american example

The transition to democratic governments in Central America over the past decade, and the subsequent emergence of institutional mechanisms for regional cooperation have greatly increased the frequency and productivity of efforts for preservation of cultural patrimony. Both the archaeological and colonial data bases overlap modern political boundaries and regional collaboration in training, pubic education, curation and research is essential. Natural forces continually impact, and human economic forces (especially international tourism) increasingly impact cultural resources. Regional cooperation in the utilization of human resources is necessary to confront the management and salvage demands of major economic development projects, and rescue efforts following natural disasters. The development of policies and programs will be effective only if matched by the growth of cultural preservation professionals in each of the Central American republics. Finally, other art consuming nations in addition to the United States must begin to respect the cultural heritage of the Central American countries and develop policies to deter abuses by diplomatic staff and employees of NGO’s (nongovernment organizations)     

Planktic foraminiferal and 13C isotopic changes across the Paleocene/Eocene boundary at Possagno (Italy)

 The interval spanning the Paleocene–Eocene (P/E) transition in the Possagno section consists of 1 m of red marls, including a 4-cm-thick, dark-red "dissolution" clay, which represents the Paleocene/Eocene boundary event. The Possagno section is much more condensed than other Tethyan and North Atlantic sections previously studied; however, in this section the most significant biotic, isotopic and sedimentological events across the P/E boundary can be recognized. The Possagno section spans the following planktic foraminiferal subzones: upper part of M. gracilis Subzone, A. berggreni Subzone, A. sibaiyaensis Subzone and probably lowermost part of P. wilcoxensis Subzone. The quantitative analysis indicates a major increase of low-latitude acarininids, including compressed tropical acarininids just above the boundary clay. This acarininid incursion begins just below the boundary clay but reaches its maximum just above the clay. The planktic foraminiferal faunal turnover is gradual except for the acarininid incursion. The isotopic results show a negative excursion in ∂¹³C values at the small benthic foraminifera mass extinction event. The acarininid maximum diversity coincides with this isotopic excursion, and reflects an increase in surface seawater temperature. Despite being very condensed, the Possagno section allows us to further confirm that the different biotic, isotopic and sedimentological events recognized in the Spanish sections (Alamedilla, Campo, Caravaca, Zumaya) are not local in nature and allows the establishment of a detailed chronostratigraphic framework to define the P/E boundary stratotype. Received: 8 April 1998 / Accepted: 12 April 1999     

Sinkhole management and flooding in Jamaica

More than 518 km² (200 mi²) of prime lands in Jamaica lay on Karstic material where sinkholes are the natural outlet of important streams. Due to increasing social pressure, the lands are inappropriately managed and as a consequence, vegetal debris and silting have plugged the sinkholes which have thus lost their capacity to drain the runoff produced during heavy rainfalls. One of these areas is Cave Valley, which during the last 36 years, has been affected by at least six floodings, some of which have produced losses of life and property, in a sector of the Jamaican population which is already under severe economic hardship. A flood prevention and mitigation project is being implemented including watershed management, river training and community preparedness. A geologic, hydrologic, and hydraulic analysis are also part of this study. All these measures are expected to reduce future losses. This article is not an official World Meteorological Organization document and WMO does not necessarily share the views expressed in it.     

Apparent damping induced by spurious pitching in shaking‐table testing

A seismic shaking‐table test performed on a one‐storey steel frame with an 8 ton RC floor slab was reproduced on a similar specimen by means of the pseudo‐dynamic (PsD) method. A satisfactory agreement of the results could only be achieved after recalibration of the theoretical mass in the PsD equation and proper inclusion in the PsD test input of the horizontal and pitching accelerations measured on the table. In the shaking‐table test, the spurious pitching motion produced a significant increase in the apparent damping that could be estimated as a function of the pitching dynamic flexibility of the system. Dynamic and PsD snap‐back tests were also performed to provide an additional check of the reliability of the PsD method. The spurious pitching motion of the shaking table should always be measured during the tests and reported as a mean to increase the reliability and usefulness of the results. Copyright © 2007 John Wiley & Sons, Ltd.     

Hybrid simulation of a multi‐span RC viaduct with plain bars and sliding bearings

This paper deals with the seismic response assessment of an old reinforced concrete viaduct and the effectiveness of friction‐based retrofitting systems. Emphasis was laid on an old bridge, not properly designed to resist seismic action, consisting of 12 portal piers that support a 13‐span bay deck for each independent roadway. On the basis of an OpenSEES finite element frame pier model, calibrated in a previous experimental campaign with cyclic displacement on three 1:4 scale frame piers, a more complex experimental activity using hybrid simulation has been devised. The aim of the simulation was twofold: (i) to increase knowledge of non‐linear behavior of reinforced concrete frame piers with plain steel rebars and detailing dating from the late 1950s; and (ii) to study the effectiveness of sliding bearings for seismic response mitigation. Hence, to explore the performance of the as built bridge layout and also of the viaduct retrofitted with friction‐based devices, at both serviceability and ultimate limit state conditions, hybrid simulation tests were carried out. In particular, two frame piers were experimentally controlled with eight‐actuator channels in the as built case while two frame piers and eight sliding bearings were controlled with 18‐actuator channels in the isolated case. The remaining frame piers were part of numerical substructures and were updated offline to accurately track damage evolution. Copyright © 2015 John Wiley & Sons, Ltd.     

Origin of boron from a complex aquifer in southeast of Spain

A study of the boron content alongside Cl ^-, SO ₄ ^2-, and NO ₃ ^- ions has enabled the factors that determine its origin to be distinguished. In carbonate rocks, with their higher saline content, boron is associated with marine intrusion. In the Plioquaternary aquifer, its origin is complex and is associated with three processes: marine intrusion, where there is a high Cl ^- content and the B/Cl ^- ratio is close to that of seawater; anthropogenic pollution, at points with high B and NO ₃ ^- concentrations and where the B/Cl ^- ratio is higher than that of seawater; and the dissolution of evaporite deposits present in the Plioquaternary strata, at a series of sampling points where the SO ₄ ^2-/Cl ^- ratio is elevated and B content is high.