These are submerged tipprold.mately i .. tl;t$ weathered granite underlying the T..ab.oretory, and are eeme11 in z eone:rete,. It is complemented by 12 struet~Jre$ of type $how. te.noos ale:ng .its lengtl'i. l) Because the stick hit. 1~1e:recover longitudinal tucU.nal restraining ett-eet$ SUJ.Yp:Q:rts can oo neglectC'tad.
The structure consisting of magnetic pole shells is related to tree and d1d. seis.'11orr1eter :rodt am1 armature assembly 13.ture is rigidly attached to: adja:ee:nt phi:r. Since increasing the current by one p~_ir .. d.if'fleulties affects the b.vis. reluctanee and historesis tl1e. Based on 1:he pl;ish- pull strt1eture or ·trt~8ducer~, the output e.m.t~ 1.s linear. displaoornent. divided by
In response to an investigation that .. will report again in another case. He found that moving the trailing end of the rod relative to the tied end causes the rod to damp.
The strain response to a pendulum having ea rm:r period i . but for terrestrial pei-iods ot l . seeont:l ,.. peri.ocls the· ratio is even greater. JJ:other ray of expression of his tlifte::rence between the two inetrtumo:nts is to nt1te tlmt t he. zontal linear $t:re.:i.n seismometer for lo~i tudinal a.r:pru:'ent $Wt'aee. Jinee equation (23) is ~.dentienl with tJ1ir; In the seismot equation there is no need to discuss the genders. Motllel? useful comb made with a g't!.lvnnometer h~v:f.ng .. period of 1.5 seconds. The quantitative response characteristic of this combination is almost the same as the short period tore it apart. (~Difference in vertical displacement of two adjacent points of' tl:tj.e c~roun.d wltose aoo:r On the one hand, engineers do not know which ground motion characteristics are responsible for the destruction, and on the other hand, seismologists do not have enough adequate seismic motion measurements to inform planning, even if the destructive characteristics are known. If we plot the maximum recorded deflection of each pendulum against its frequency, we get a curve that can be called the undamped oscillation spectrum of an earthquake (see Figure 1). Specifically, the seismic destructiveness is the integral over the pendulum frequency of the maximum displacement of an infinite set of undamped pendulums spanning a significant range of frequencies. Therefore, if its frequency is known, the maximum displacement of its center of oscillation is given by the observed amplitude of the pendular spectrum at the same frequency. It is clear that if the resonant force acts in a time interval which is short compared to the time constant of the system, the resulting amplitude is independent of the damping. Therefore, we can expect the structural vibration amplitudes to be essentially independent of the damping. Younger, "Stresses in a Vertical Elastic Rod When Subjected to a Harmonic Motion of One End," Bidletin of the Seismological Society of America, 22, 1, March, 1932. Observations with a set of seismographs constructed by the writer for use by Professor Martel of the California Institute of Technology showed that the tops of buildings have about three times the amplitude of vibrations than the ground at the bases. Based on these experiments, we can expect the undamped oscillation spectrum to have amplitudes about three times larger than the corresponding damped spectrum. It may be well to consider some of the characteristics of seismic pendular spectra that can be predicted based on current knowledge. A free vibration of the ground will be indicated by a sharp maximum in the undamped spectrum, which does not occur in the damped spectrum. This will be true regardless of whether the free vibration exists in the region of the focus or in the region of the observing station. 34;Theory of Elastic Systems Vibrating under Transient Impulse, with an Application to Earthquake Proof Buildings," Proceedings of the National Academy of Scimces and M. From Equation 1 we find that a single component of the seismic disturbance is given by. A M etod i'o:r the instrumental determination of the:B:extent of 'faulting. tt if a fault displacement is clearly visible at the surface of the soil .. there is no difficulty in measuring it. W ood and Hiehte'.r, are located a few ldlo- met-ers from the eoe at l~Grv1port • . fil1 instrumental ~:Pieenter . determined. as this one was, with the arrival t:lmes of the first waves, gives no evidence about the e:ictent of displacements or the .. point from which marlmtm1 radiates energy. It is so clear from a simple inspection of the seis.rnograms that the prinei:pal shock. A rather rough but definite instrumental indication of .. or extension of faults is given by the eo:mpa:difference in the periods of the seismic waves in the main shock and those in the a.:f'tershoeks. .. the main shock was recorded on the strong motion seism .. . a graph that has :per:tod .10 seconds, eri tioal darn.ping , ,. and mag~. aftershocks were recorded on a torslon: seismograph which had essentially the same eonstantes with the exception of the l'naf':)lifioation which was about 600. As the stresses increase there comes a time when the stress at some point exceeds the cohesive strength of the fault and consequently t\"·10 fault surfaces slide past each other. The immediate effect of the longitudinal wave is to increase the existing strains at adjacent points along the fault. 2 where the a.now the direction of :movement of the ground part indimrue,., ieles 1n the wava•fl"t;nt. The displacement velocity must be nec.- essnri l:y le, ss as t;1e longitudinal wave velocity; sine the wa.ve•f:ront : ts not rectangular and in c:.onsequenee a finite time is required for the incremental st:t"ess to build UlJ to the sliding value. Since the 'faulting veloci t-Y does not differ greatly from the wave velocity • the elen1entary waves generated from successive slip points are approximately 1.n phase and consequently their. Under such circumstances; the ine::restorative voltage generated by the v1raves may be su:tf'ieient to cause the fault movement to overshoot the equilibrium. If the mechanism of error just described is correct, the observed events at a given station can be determined in advance with the aid of the diagram. A wave of displacements is generated and proceeds along the fa~tlt with a velocity v 1 r. So the shifting movement will arrive. As the assumed rate of faulting is reduced, the corresponding ellipses become smaller until eventually a limit is reached where the ellipse is just tangential to the fault. Although it is known that the rate of faulting is less than the rate of longi tudj.nal wa,res, it is pre. Accordingly, the extent of faulting is determined only aAi to upper and lower limits. However, in the case of the Long Beach earthquake, there is evidence that the upper limit is the actual limit of faulting. ,. It is therefore :rea.able to believe that during the main earthquake, the :fault movement actually exceeded the equilib:ri.um. The number that fell in one direction was considerably greater than the nll111ber that fell in the other direction. It is clear that all but one of the cemeteries indicate directions in excellent agreement with the results of this paper.3etting
1) - Hence
