The Demand For Cigarettes and Restrictions on Smoking in the Workplace

The purpose of this paper is to empirically test the effect that restrictive clean air laws have on the level of smoking. Restrictive clean air laws refers to the laws which prohibit smoking in private workplaces as well as in public places. The data employed in this study consist of a time series of cross sections of the fifty states of the U.S., and Washington D.C., over the time period from 1975 through 1985, Since states where sentiment is strongly against cigarettes are more likely to pass a clean air law, endogeneity between cigarette demand and the clean air law is a problem. A two step estimation model is used to control for endogeneity. Both a single equation and a two equation model of cigarette demand were estimated. The single equation results indicate that a clean air law has a significant negative effect on cigarette demand. However, the two equation model indicates that cigarette demand has a significant negative effect on the probability of passing a clean air law. The results indicate that when endogeneity is controlled for the clean air law dose not have a significant effect on cigarette demand. This does not imply that the enactment of a clean air law would not reduce the level of smoking if such a law were imposed in all states, but rather that only states with low levels of smoking are able to pass restrictive clean sir laws.

Alcohol Control Policies and Motor Vehicle Fatalities

The purpose of this study is to estimate the effects of drunk driving deterrents and other alcohol related policies on drunk driving. The data set employed is an annual time-series of state cross-sections for the 48 contiguous states of the U.S. from 1982 through 1988. Total and alterative alcohol involved motor vehicle fatality rates, for the general population and for 18 to 20 year olds, are used as measures of drunk driving. The results indicate that the moat effective policies are increased beer taxes and mandatory administrative license actions. Maintaining the beer tax at its real 1951 value would have reduced fatalities by 11.5 percent annually, on average, during the sample period. A mandatory administrative license sanction of one year would have reduced fatalities by 9 percent. The next most effective policies are a 21 year old legal drinking age, preliminary breath test and dram shop laws and relatively large mandatory fines. These policies each reduce total fatalities by about 5 to 6 percent. No plea bargaining provisions and mandatory license sanctions upon conviction are also found to have some deterrent effect. Other drunk driving laws tested include mandatory jail sentences and community service options, illegal per se laws, and open container laws. None of these were found to have a deterrent effect on drunk driving.

Laboratory observations of slow earthquakes and the spectrum of tectonic fault slip modes

Slow earthquakes represent an important conundrum in earthquake physics. While regular earthquakes are catastrophic events with rupture velocities governed by elastic wave speed, the processes that underlie slow fault slip phenomena, including recent discoveries of tremor, slow-slip and low-frequency earthquakes, are less understood. Theoretical models and sparse laboratory observations have provided insights, but the physics of slow fault rupture remain enigmatic. Here we report on laboratory observations that illuminate the mechanics of slow-slip phenomena. We show that a spectrum of slow-slip behaviours arises near the threshold between stable and unstable failure, and is governed by frictional dynamics via the interplay of fault frictional properties, effective normal stress and the elastic stiffness of the surrounding material. This generalizable frictional mechanism may act in concert with other hypothesized processes that damp dynamic ruptures, and is consistent with the broad range of geologic environments where slow earthquakes are observed

Evolution of elastic and mechanical properties during fault shear. The roles of clay content, fabric development, and porosity

Phyllosilicates weaken faults due to the formation of shear fabrics. Although the impacts of clay abundance and fabric on frictional strength, sliding stability, and porosity of faults are well studied, their influence on elastic properties is less known, though they are key factors for fault stiffness. We document the role that fabric and consolidation play in elastic properties and show that smectite content is the most important factor determining whether fabric or porosity controls the elastic response of faults. We conducted a suite of shear experiments on synthetic smectite-quartz fault gouges (10–100 wt% smectite) and sediment incoming to the Sumatra subduction zone. We monitored Vp, Vs, friction, porosity, shear and bulk moduli. We find that mechanical and elastic properties for gouges with abundant smectite are almost entirely controlled by fabric formation (decreasing mechanical and elastic properties with shear). Though fabrics control the elastic response of smectite-poor gouges over intermediate shear strains, porosity is the primary control throughout the majority of shearing. Elastic properties vary systematically with smectite content: High smectite gouges have values of Vp ~ 1,300–1,800 m/s, Vs ~ 900–1,100 m/s, K ~ 1–4 GPa, and G ~ 1–2 GPa, and low smectite gouges have values of Vp ~ 2,300–2,500 m/s, Vs ~ 1,200–1,300 m/s, K ~ 5–8 GPa, and G ~ 2.5–3 GPa. We find that, even in smectite-poor gouges, shear fabric also affects stiffness and elastic moduli, implying that while smectite abundance plays a clear role in controlling gouge properties, other fine-grained and platy clay minerals may produce similar behavior through their control on the development of fabrics and thin shear surfaces

The role of deformation bands in dictating poromechanical properties of unconsolidated sand and sandstone

Cataclastic shear bands in sands and sandstones are typically stronger, stiffer, and exhibit lower permeability than the surrounding matrix, and therefore act as barriers to fluid flow. Previous work has quantified the reduction in permeability associated with these features; however, little is known about the role of shear band structure in controlling the way they impact permeability and elastic properties. Here, we report on a suite of laboratory measurements designed to measure the poromechanical properties for host material and natural shear bands, over effective stresses from 1–65 MPa. In order to investigate the role of host material properties in controlling poromechanical evolution with stress, we sampled shear bands from two well-studied sandstones representing structurally distinct end-members: a poorly cemented marine terrace sand from the footwall of the McKinleyville thrust fault in Humboldt County, California, and a strongly-cemented sandstone from the hanging wall of the Moab Fault in Moab, Utah. The permeability-porosity trends are similar for all samples, with permeability decreasing systematically with increasing effective stress and decreasing porosity. The permeability of the host material is consistently >1 order of magnitude greater than the shear bands for both localities. For the unconsolidated case, shear bands are less permeable and stiffer than the host material, whereas for the consolidated case, shear bands are slightly less permeable, and wave speeds are slower than in the host. We attribute the differences between the McKinleyville and Moab examples to changes in structure of the nearby host material that accompanied formation of the shear band