Gravity surveying, or prospecting, is a method for investigating subsurface bodies or structures that have an associated lateral density variation. These include ore bodies and intrusions whose density differs from that of the surrounding rocks, basins infilled with less dense rocks, faults if they offset rocks so that there are lateral density differences, and cavities.

Gravity surveys measure minute differences in the downward pull of gravity and so require extremely sensitive instruments. Gravity readings also depend on factors that have nothing to do with the subsurface rocks, and corrections for their effects are very important.

The resistivity of rocks usually depends upon the amount of groundwater present and on the amount of salts dissolved in it, but it is also decreased by the presence of many ore minerals and by high temperatures

The main uses of resistivity surveying are therefore for mapping the presence of rocks of differing porosities, particularly in connection with hydrogeology for detecting aquifers and contamination, and for mineral prospecting, but other uses include investigating saline and other types of pollution, archaeological surveying, and detecting hot rocks.

Resistivity surveying investigates the subsurface by passing electrical current through it by means of electrodes pushed into the ground. Traditionally, techniques have either been designed to determine the vertical structure of a layered earth, as vertical electrical sounding, VES, or lateral variation, as electrical profiling; however, more sophisticated electrical imaging methods are being increasingly used when there are both lateral and vertical variations.

We are increasingly aware that we should not take our environment for granted. Part of the concern is about damage caused by human activity; part is the realisation that nature is not always benign and may produce catastrophes to which we are increasingly vulnerable as populations grow and modern civilisation with its industry and transport systems becomes more complex. Some of these catastrophes can be investigated by solid earth geophysics, notably earthquakes (discussed briefly in Section 5.10) and volcanoes.

Volcanoes can inflict great catastrophes on mankind. Historically, they have caused far fewer deaths than earthquakes (or storms or flooding), but this may not be true in the future, for the geological record reveals vastly greater eruptions in the past. For example, the 1980 eruption of Mt. St. Helens, cause of the greatest volcanic damage in the United States in the 20th century, erupted 1 km3 of material, but in 1783–1784 Laki, Iceland, poured out 15 km3 of basalts, and Krakatoa in 1883 blew out a similar volume, while in 1815 Tambora, Indonesia, erupted about 50 km3 of magma. But 700,000 years ago, the Long Valley Caldera of California (not yet extinct!) discharged 500 km3 of ash, and even larger eruptions have occurred. In contrast, it is unlikely that tectonic earthquakes much larger than those experienced this century can occur.

On the brighter side, eruptions rarely occur without being preceded by increased activity long enough in advance to allow time for evasive action, one reason for their relatively low death count. …

Civil engineering often needs detailed information about the subsurface before starting construction of dams, bridges, roads, airports, buildings, tunnels, and so on. In the past, site investigation relied heavily on drilling, but though drilling can provide essential information it can miss important features between boreholes, and it does not give information about hazards such as earthquakes. A better strategy is first to carry out a combined geological and geophysical survey, and then concentrate drilling where the survey shows it will be most useful. For successful results, geophysicists and geologists need to be clear what information the engineer needs, while the engineer needs to understand what kinds of information the geophysicist and geologist can offer, and their limitations.

Applications where geophysics can be of use to civil engineers include mapping earthquake probability and severity; measuring the depth of unconsolidated cover or weathering, or the extent of infilling; detecting fracture zones; finding pipes and buried objects; locating voids, caves, and old mine workings; and investigating contaminated ground. Some of these have already been considered briefly, such as earth quakes (Chapter 5) and contaminated ground (Section 26.7). This chapter considers only the investigation of cavities and voids, which offers straightforward applications of geophysics.

Temperature generally increases with depth in the Earth, and this is responsible for the maturation of hydrocarbons, many forms of mineralisation, thermal metamorphism and, of course, volcanism and other igneous activity. At sufficient depth, rocks are too hot to fracture and deform ductilely, while at even greater depths they are hot enough to flow like a very viscous liquid. It is this ability to flow that allows the Earth to be an active planet, with mountain building, earth quakes, and plate tectonics; without its hot interior the Earth would be a dead planet, like the Moon.

To understand these processes we need to know the temperatures at different depths within the Earth. Unfortunately, there is no direct way of measuring temperature below the few kilometres that boreholes reach, and temperatures at greater depths are mainly inferred from measurements of the temperatures and thermal properties of rocks near the surface.

Radioactivity surveying measures the natural radioactivity due to potassium, thorium, and uranium in near-surface rocks, which has applications in geological and geochemical mapping, and is used to find ores of uranium and thorium or other types of ore that have associated radioactivity. It also has environmental applications, mapping radon, a hazard to health, in surface rocks and waters.

The most common surveying method detects γ rays, which can be used to identify the source element as well as detect the presence of radioactivity, and can be employed in ground or airborne surveys, but radon measurement often requires sampling below the surface.

ABSTRACT. The evaluability hypothesis posits that when two objects are evaluated separately, whether a given attribute of the objects can differentiate the evaluations of these objects depends on whether the attribute is easy or difficult to evaluate independently. The article discusses how the evaluability hypothesis explains joint-separate evaluation reversal, which is the phenomenon that the rank order of the evaluations of multiple objects changes depending on whether these objects are evaluated jointly or separately. The article presents empirical evidence for the evaluability hypothesis. The final section of the article discusses implications of the hypothesis for issues beyond reversals - in particular for inconsistencies between decisions and their consequences. Decisions are typically made in the joint evaluation mode, and the outcome of a decision is usually experienced (or “consumed”) in the separate evaluation mode. Thus, reversals between joint and separate evaluation may manifest themselves in decision-consumption inconsistencies.

ABSTRACT. The standard theory of choice -based on value maximization-associates with each option a real value such that, given an offered set, the decision maker chooses the option with the highest value. Despite its simplicity and intuitive appeal, there is a growing body of data that is inconsistent with this theory. In particular, the relative attractiveness of x compared to y often depends on the presence or absence of a third option z, and the “market share” of an option can actually be increased by enlarging the offered set. We review recent empirical findings that are inconsistent with value maximization and present a context-dependent model that expresses the value of each option as an additive combination of two components: a contingent weighting process that captures the effect of the background context, and a binary comparison process that describes the effect of the local context. The model accounts for observed violations of the standard theory and provides a framework for analyzing context-dependent preferences.

KEY WORDS decision making; consumer choice; independence of irrelevant alternatives

ABSTRACT. An important idea, which characterizes law in society, is a reluctance to move from the status quo. In general, one can argue that legal institutions and legal doctrine are not engaged in the redistribution of wealth from one party to another. This paper explores a possible explanation for that principle. The authors' research suggests that, across a wide range of entitlements and in a variety of contexts, individuals value losses more than forgone gains. The paper argues, as a matter of efficiency, that law and social policy might have developed in a manner consistent with this valuation disparity. Furthermore, this valuation disparity can be transformed into conceptions of fairness, and, as a matter of fairness, legal decisions might have developed in a manner consistent with this fairness norm. In the first part of the paper, the economic and psychological research on the valuation disparity is described in detail. The paper then examines a series of legal doctrines, all of which can be explained by the valuation disparity phenomenon revealed in the experimental data. Cohen and Knetsch conclude that the behaviour of legal institutions and actors can be explained by the valuation disparity.

ABSTRACT. The term money illusion refers to a tendency to think in terms of nominal rather than real monetary values. Money illusion has significant implications for economic theory, yet it implies a lack of rationality that is alien to economists. This paper reviews survey questions, which are designed to shed light on the psychology that underlies money illusion, regarding people's reactions to variations in inflation and prices. We propose that people often think about economic transactions in both nominal and real terms and that money illusion arises from an interaction between these representations, which results in a bias towards a nominal evaluation.

“A nickel ain't worth a dime anymore.”

We have standardized every other unit in commerce except the most important and universal unit of all, the unit of purchasing power. What business man would consent for a moment to make a contract in terms of yards of cloth or tons of coal, and leave the size of the yard or the ton to chance? … We have standardized even our new units of electricity, the ohm, the kilowatt, the ampere, and the volt. But the dollar is still left to the chances of gold mining.