Source and Propagation Effects of Rayleigh Waves from Central Asian Earthquakes

Patton, Howard J.

doi:10.21236/ada070241

Cited by 19 publications

(15 citation statements)

References 38 publications

(58 reference statements)

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“…No thick highvelocity 'lid' is required by the data as in the east-central United States. Note that such a feature has been suggested by several authors for regions close to the path under study(Crampin 1966; Levshin & Berteussen 1979;Patton 1978; McCowan, Glover & Alexander 19 78).…”

mentioning

confidence: 57%

“…13). A four-eigenvector model obtained for the United States (Cara 1979) and the two models obtained by Patton (1978) in northern Eurasia are also shown.…”

Section: Low Velocity Zonementioning

confidence: 98%

“…Finer structures should be resolved with more accurate phase-velocity data but the horizontal 'resolving power' of the method is very poor in the case of northern Eurasia: because of the length of the path, it is difficult to say if the non-existence of thick high velocity lid is due to the stable northern platform of northern Eurasia or if it results from an averaging process between possible low S velocities in the first part of the path near Japan or in the Barents Sea (Levshin & Berteussen 1979) and higher velocities in the shield area of northern Eurasia. In order to check the last question one can compare our results with those obtained by Patton (1978) from the fundamental Rayleigh mode in the 'northern platform and shield' of Eurasia (model A in Fig. 13) and in the 'coastal plains and forelands' of Eurasia (model B, Fig.…”

Section: Low Velocity Zonementioning

confidence: 99%

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New inferences from higher mode data in western Europe and northern Eurasia

Cara¹,

Nolet²,

Nercessian³

1980

Geophys J Int

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Summary Stacking methods applied to wide arrays of long period stations provide a powerful tool to investigate the physical properties of the upper mantle by means of higher modes. In this paper, the UC‐diagram technique of Cara (1976) is applied to a subset of records first used by Nolet (1975, 1976) to determine the dispersion of higher Rayleigh modes in western Europe. For the fundamental and first higher modes, the phase velocities found in the present study are very similar to those first obtained by Nolet (1976) but the second made exhibits slightly higher velocities in the period range 35–55 s. As a consequence, the low density channel proposed by Nolet (1977) under western Europe is no longer necessary to explain the higher mode data and further investigation will be necessary to obtain more details in the density distribution with depth. A new set of higher Love mode phase velocities has been also obtained in western Europe. As it has already been observed for the fundamental mode in several parts of the world, the phase velocities found here for the first and second higher modes are too large compared to those predicted by the models fitting the Rayleigh mode data. It is very difficult to interpret both the Love and Raylcigh wave data in terms of isotropic S velocity distribution and an anisotropy of the elastic parameters of the upper mantle is probable under western Europe. Another wide continental region, northern Eurasia, is investigated from higher Rayleigh mode phase velocities measured for the path between northern Japan and western European stations. A nearly constant 4.5–4.6 km s−1S velocity is required by these data in the uppermost 200 km of the upper mantle. Unlike the higher mode data obtained for the central and eastern United States by Cara (1978) or for western Europe in this paper, no wide low velocity channel is necessary to explain the higher mode data in this large arca.

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mentioning

confidence: 57%

“…13). A four-eigenvector model obtained for the United States (Cara 1979) and the two models obtained by Patton (1978) in northern Eurasia are also shown.…”

Section: Low Velocity Zonementioning

confidence: 98%

Section: Low Velocity Zonementioning

confidence: 99%

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New inferences from higher mode data in western Europe and northern Eurasia

Cara¹,

Nolet²,

Nercessian³

1980

Geophys J Int

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“…Surface wave analysis shows that depths for three shocks in this area are less than about 15 km [Patton, 1978]. No pP phases were unambiguously reported and we are not aware of evidence for subcrustal seismicity in the Markansu Valley region.…”

mentioning

confidence: 71%

“…Khalturin et al, 1977]. are essentially those given by Patton [1978] . He inverted Rayleigh wave spectra to obtain moment tensors for these events, and the corresponding fault plane solutions agree remarkably well with the P wave first motions.…”

Section: Discussion Of the Mainshockmentioning

confidence: 97%

Characteristics of foreshocks and short-term deformation in the source area of major earthquakes

Molnár¹

1981

Open-File Report

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We have examined the locations and radiation patterns of the foreshocks to the 4 February 1978 Haicheng earthquake. Using four stations, the foreshocks were located relative to a master event. They occurred very close together, no more than 6 kilometers apart. Nevertheless, there appear to have been too clusters of foreshock activity. The majority of events seem to have occurred in a cluster to the east of the master event along a NNE-SSW trend. Moreover, all eight foreshocks that we could locate and with a magnitude greater than 3.0 occurred in this group. The're also "appears to be a second cluster of foresfiocks located to the northwest of the first. Thus it seems possible that the majority of foreshocks did not occur on the rupture plane of the mainshock, which trends WNW, but on another plane nearly perpendicualr to the mainshock. plane. This inference is supported by differences among the radiation patterns of the foreshocks.We also examined the radiation patterns of the foreshocks, primarily through the amplitude ratios of P and S waves (Ap/As) recorded at each station. While the ratios were relatively constant at the more distant (A=100-200 kilometers) stations, two very different waveforms were recorded throughout the sequence at Yingkou (A=20 kilometers). Calculations of the amplitude ratios expected from the (not very different) fault plane solutions of the mainshock and some of the largest foreshocks showed that two different waveforms should be recorded at Yingkou. A definite correlation could not be made between the two mechanisms and the different location clusters. 1) IntroductionThe successful prediction of the 4 February, 1975 Haicheng earthquake (M=7.3) was due, in a large part, to the occurrence of a large f oreshock sequence of more than 500 events in the four days preceding the mainshock (Wu, 1976). Such a large sequence is a rare event -indeed, the Haicheng series is the only large foreshock sequence to have been well recorded -and we cannot hope that many other mainshocks will have such sequences. Many large earthquakes are preceded by a few foreshocks (Jones and Molnar, 1979) but so far we have been able to recognize them only in hindsigl}£. To increase the number of earthquakes that can be successfully predicted, we need to learn how to differentiate foreshocks from "normal" earthquake swarms before the mainshock occurs and when the shear number of events is not an overpowering consideration as it was at Haicheng. But precisely because ofits great length, the Haicheng sequence provides a unique opportunity to study this problem. The large number of events allows the characteristics of "this foreshock sequence to be seen more clearly. These characteristics could then be compared with those of earthquake swarms to the benefit of all people engaged in earthquake prediction research. Thus, the first part of the Chinese-American exchange in earth sciences has been a study of the Haicheng foreshock sequence resulting in this report.There are two purposes of this research. There is,...

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