Preface

We start from the assumption that social interaction in informal conversation between family members and friends is organized in fundamentally similar ways in the languages and cultures of the world (Stivers et al. 2009). For our examination of how interaction is conducted with linguistic (and other) resources, we can thus rely on the descriptive categories developed in conversation analytic studies of talk-in-interaction. These serve as a tertium comparationis (basis of comparison) and can be underpinned with detailed studies of the linguistic (and other) resources deployed to realize them. This is what practitioners of Interactional Linguistics have been doing since about the middle of the 1990s, for English and other languages.

In this part of the book we begin with interaction and ask how it is conducted with linguistic (and other) resources, comparing as far as possible the organizational details of talk in different languages. We start with the most basic mechanisms of conversation: turn construction and turn taking (Chapter 2) and repair (Chapter 3). We then turn to action formation and ascription (Chapter 4), followed by topic management and sequence organization (Chapter 5). In addition, in Online-Chapter B we deal with preference, and in Online-Chapter C we examine the display of stance and footing. In Online-Chapter D we discuss an interactional linguistic perspective on storytelling as a “big package”.

Prior to embarking on these topics, however, a clarification of terminology is in order.

If we assume that participants’ construction and co-construction of actions is what interaction is primarily about, what, then, is an action? Do all utterances in talk-in-interaction perform actions? If not, what other categories do we need? (For more detail on actions and action formation see Chapter 4.) Conversation Analysis distinguishes actions from the practices that are used to accomplish them (Schegloff 1997a). The action of initiating repair, for instance, is ordinarily associated with the use of questioning items such as huh?, who?, etc. and certain forms of repeats. When such formats are deployed for initiating repair, this is described as a practice.

Up to this chapter, we have considered the motion produced by earthquakes from the point of view of wave propagation and free oscillations, without considering its origin. Chapters 16 to 20 are dedicated to this subject, that is, the earthquake source, its location, size, and mechanism. As we saw in Chapter 2, most earthquakes are tectonics and caused by sudden motion along faults which releases accumulated tectonic stresses and produces seismic waves. The source of an earthquake can then be considered to be the product of rupturing of a particular fault with a relative displacement of its two sides and release of the accumulated elastic strain that had been produced by tectonic processes. However, as a first approximation, we can consider the source of an earthquake as a point, called its focus, from which seismic waves are generated and propagated. The reduction of the focus to a point is called the point-source approximation, which is valid if observation points are at a sufficiently large distance compared with source dimensions, and wave lengths are also large. The simplest point source model is the isotropic point source, in which the source is considered as a point from which waves propagate with equal amplitude in all directions. In Chapter 2 we have already seen in a descriptive form the problem of the location, time, and size of earthquakes. In this chapter we will quantify this knowledge, defining the focal parameters of earthquakes and their determination, such as location and origin time, the different ways of measuring their size, defining the concepts of intensity and magnitude, and also those of seismic moment and stress drop.

Location of an earthquake focus

The location of the point focus of an earthquake in space and time is given by its geographic coordinates (x0, y0), its depth (z0), and the time of occurrence or origin time (t0). Owing to the dimensions of the actual source, the focal coordinates refer to a certain point, for example, where rupture starts, and the origin time refers to the initiation of the faulting process. The definitions of the parameters of the focal location use this point approximation.

In Chapters 8 to 10, using ray theory, we have seen how travel time curves depend on the characteristics of the media through which the seismic waves propagate and in consequence that the velocity distribution with depth can be deduced from them. In this chapter we will apply these results to observations of wave propagation in the Earth and discuss the results concerning its internal structure. Thus we will see how we obtained the knowledge about the structure of the Earth that we introduced in Section 2.6. For short distances (less than 1000 km) we can use the flat-Earth approximation and plane geometry. Seismic waves for that range of distances give information on depths of about 100 km, that is, of the crust and part of the upper mantle (lithosphere). For this range of distances we can apply the theory derived in Chapters 8 and 9. For greater distances the spherical shape of the Earth must be considered, so the results of Chapter 10 must be applied. The effects due to the deviations of the form of the Earth from a sphere, that is, mainly its flatness, can be taken into account by using corrections to the spherical model. In seismology these effects are not very important.

Observations and methods

The first seismic waves used for the study of the Earth's structure were those produced by earthquakes. Even today this is the main source of information, especially for the deep interior. Among the first tables and curves of travel times of seismic waves were those of Oldham, who in 1906 deduced the existence of the Earth's core. These tables were completed by Zöppritz and Herbert H. Turner and later, in 1914, by Gutenberg. In 1940, Jeffreys and Bullen published their tables of travel times which are very widely used, even today (Jeffreys and Bullen, 1940). In 1968, Eugene Herrin published tables of travel times for P waves only (Herrin, 1968). On a recommendation from the IASPEI, travel time tables have been derived from a spherically symmetric velocity model, known as iasp91, based on modern data (the ISC catalog 1964–88) (Kennett and Engdahl, 1991).