Seismicity of the Earth

Abstract

Finally, in the geographical discussion, a limited use has been made of macroseismic and historical data. Sieberg (1932a) has been consulted throughout. Isobaths on the regional maps and terminology of oceano graphic features are based on Vaughan, et al. (1940). DEEP-FOCUS EARTHQUAKES This section revises and extends the results reported by Gutenberg andRichter in two previous papers (1938; 1939), to which the reader is referred for sources of the material used and for discussion of methods. In addi tion, recent deep shocks in the Japanese area have been checked against a list by Wadati (1939) for the years 1934-1938. New determinations of deep-focus earthquakes are given in Tables 1 and 2. All epicenters of deep-focus shocks now known to the authors are plotted in Figure l .2 They are also plotted, together with normalshocks, on the regional maps (Figs. 3-14).The general characteristics of the distribution of deep shocks are as described in earlier papers. A few individual shocks call for special comment. No. 3 p is in a new location near Barbados.No. 81 M is the first shock with depth in excess of 300 kilometers to be located in the New Hebrides area.Nos. 133 g and 133 i constitute an important southern extension of the line of inter mediate shocks on Luzon.2Maps used in this paper were drafted by Mr, John M. Nordquist. The world maps, Figures 1 and 2, are of his own design. The purpose was to construct a map which would present all the principal seismic areas and belts without excessive distortion or interruption. These world maps are not on any projection in the restricted sense; the meridians are drawn as circles, and divided proportionately into arcs through the ends of which the parallels are drawn.

The quest for wisdom: lessons from 17 tsunamis, 2004–2014

“…In lay words, this amounts to saying that 'all fault zones (perhaps, all rocks) are created equal', and that specific seismic source parameters, such as the amount of seismic slip u, should all be predictable from the knowledge of just one number, the source size, in physical terms its seismic moment M 0 , which can be expressed under the concept of a moment magnitude M w [24]. This paradigm has been generally supported by a remarkable observational dataset covering more than 17 orders of magnitude in seismic moment [25], and has proven very seminal, as it can explain, for example, the frequency-magnitude distributions noticed empirically by Gutenberg & Richter [26], and explained in this context by Rundle [27]. However, the recognition of 'tsunami earthquakes' by Kanamori [28] pointed to an obvious diversity in strain release and hence to a violation of the concept of seismic similitude by this class of events, which are defined as triggering tsunamis of greater amplitude than expected from their magnitudes, especially conventional ones ('tsunami earthquakes' are characterized by source spectra displaced towards low frequencies [29,30]).…”

“…It has now been 10 years since the Sumatra-Andaman earthquake of 26 December 2004 generated what was probably the most lethal tsunami in the history of mankind, with a death toll generally estimated at more than 225 000. A major cause of this horrific number was the total lack of preparedness, or even awareness a tsunami potential restricted to the near field, whereas the latter can result in catastrophic transoceanic tsunamis.…”

Magnitudes of great shallow earthquakes from 1953 to 1977

“…As originally defined by Richter (1935), magnitudes for local earthquakes, ML, were calculated from amplitudes on Wood-Anderson torsion instruments. Gutenberg and Richter (1936, 1941, 1942 published several intermediate reports on amplitudes and magnitudes. Gutenberg (1945a, b, c) defined surface-wave magnitudes, Ms, and body-wave magnitudes, rob.…”

Thickness Of The Earth's Crust Beneath The Pacific-Antarctic Ridge

“…The focal depths of the earthquakes studied in this paper are not known accurately enough to confirm the suggestion of Bath and Vogel, but the similarity of the paths from the two groups of earthquakes suggests that the predominance of a single type of dispersive wave is associated with the characteristics of the source rather than with those of the path. Gutenberg and Richter (1954) give an equation, log N = aI+b(S-M), connecting the magnitude (M) with the number of earthquakes (N) in a magnitude interval of 0'1. The relation is described by the coefficients a and b, and in particular b gives the rate of decrease in the number of earthquakes with increasing magnitude.…”