Comments on 'P-wave amplitudes in the United States: east--west variations and variability', by Rhett Butler

Der, Zoltan A.

doi:10.1111/j.1365-246x.1985.tb06407.x

Geophysical Journal International

1985

DOI: 10.1111/j.1365-246x.1985.tb06407.x

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Comments on 'P-wave amplitudes in the United States: east--west variations and variability', by Rhett Butler

Zoltan A. Der¹

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1985

1987

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Cited by 3 publications

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“…By studying Q,, and Q, independently we can hope to determine the true relationship between Q, and Q,. Plausible Q mechanisms such as bulk dissipation and scattering do not follow the empirical relationship (t,*-4tE) stated by Der (1985).…”

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confidence: 85%

“…Extreme amplitude variations do exist between certain areas of the US and Canada, particularly between the Rocky Mountain front and the Canadian shield. Der (1985) criticizes the lack of discussion of features smaller than the east-west scale. However, the central thesis of Butler (1984b) was to determine the difference of the means of two population distributions of characteristic P-wave amplitudes: seismic stations in the east compared with stations in the west.…”

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confidence: 99%

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P-wave amplitude variation between the eastern and western United States: reply to Z. A. Der

Butler

1985

Geophysical Journal International

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confidence: 85%

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confidence: 99%

P-wave amplitude variation between the eastern and western United States: reply to Z. A. Der

Butler

1985

Geophysical Journal International

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Structure of the Earth: Mantle and core

Lay¹

1987

Reviews of Geophysics

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The deep interior structure of the earth has been extensively analyzed using a wide variety of seismic phases and techniques during the last four years. Most studies have emphasized quantitative three‐dimensional mapping of the lateral velocity heterogeneity of the mantle and core. These aspherical velocity variations are believed to be direct manifestations of thermal and compositional heterogeneity associated with convective processes. A first generation of global models for the lateral velocity variations in the deep earth has been produced, providing tantalizing images of large scale structures suggestive of a non‐steady state thermal convection system. The upper 400 km of the mantle has the strongest lateral velocity variations, of up to ±10% for shear velocity. Surface‐wave analyses that do not require a priori regionalizations have demonstrated that there is a strong association between surface tectonic provinces and the uppermost mantle velocity variations. Thus, the thermal and convective state of the upper 200 km of the mantle can be reliably interpreted in the context of plate tectonics. The upper mantle models support the contention that continents have deep roots, with differences in velocity structure from oceanic and active tectonic regions extending as deep as 400 km. Very long‐wavelength lateral velocity variations of a few percent have been detected in the transition zone at depths from 400 to 670 km, as well as throughout the lower mantle. These deep‐seated variations have little correspondence to surface tectonics, and efforts to interpret their nature are just beginning. The lowermost 200 km of the mantle (D″ region) has lateral velocity fluctuations comparable to those in the upper mantle, and evidence has been presented for the presence of a sizable velocity discontinuity at the top of the D″ layer. A combined thermal and compositional boundary layer, roughly mirroring the lithosphere, is a likely explanation for this anomalous zone. The core‐mantle boundary appears to have significant (10 km) long‐wavelength topography, presumably sustained by dynamic stresses from deep mantle convection. The inner core may have strong lateral heterogeneity or axially symmetric anisotropy, suggesting a complex thermal and compositional state. Significant progress has been made in characterizing the frequency dependence of anelastic attenuation in the mantle in the short‐period body‐wave band. Models for teleseismic P‐wave attenuation operators have converged, with t* values of 0.7–1.0 s appropriate at 1 Hz, and t* values of 0.4–0.6 s appropriate at 4 Hz. Regional variations of attenuation are slowly being mapped out as well.

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Underground nuclear explosions: Verifying limits on underground testing, yield estimates, and public policy

Sykes¹

1987

Reviews of Geophysics

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The period 1982 to 1986 has seen greatly increased activity in a number of problems related to the verification of nuclear test ban treaties. The greater activity results from a combination of scientific advances, major decisions by the United States Government about the negotiation of test ban treaties, the Soviet moratorium on testing, and much greater interest by the U.S. Congress in nuclear testing, test bans and other aspects of arms control. This review seeks to cover a range of activity that extends from scientific research to governmental decisions and public policy. A major aim has also been to provide a detailed bibliography on what is a wide range of topics. It is still not complete for what is a huge so-called "gray literature" of reports to various government agencies. The discussion that follows only covers a selected number of these publications and reports.The last four years have seen major research on the utilization of high-frequency seismic waves, the characterization of seismic sources as being either of the earthquake or explosion type using greater amounts of the information contained in the seismogram, increased use of digital data, the estimation of yields of Soviet weapons tests, debate about whether the Soviet Union has complied with the existing Threshold Test Ban Treaty, the use of regional seismic waves for yield estimation and source characterization, renewed interest in the problem of seismic decoupling for explosions detonated in large cavities, and the emergence of global seismic networks in which data can be transmitted rapidly by satellite in digital form. Political and International ConsiderationsActive interest in a Comprehensive Test Ban Treaty (CTBT) is now more than 30 years old. A CTBT, which still does not exist today, is one of the longest running issues in the arms control field. Seismology provides the main tools for the detection of underground atomic testing, for the identification of signals from an event as being from either an underground test or an earthquake, and for accurate estimates of the yields of underground nuclear explosions. The United States and several other countries have conducted extensive programs to improve the detection of nuclear tests for more than 27 years. The United States has spent about a half billion dollars in this endeavor, and more than a billion dollars has been spent worldwide. The verification of atomic testing is one of the prime areas in which geophysicists interact with the formulation of public policy on important issues of national and international concern.The United States, the Soviet Union and more than 120 other countries signed the Limited Test Ban Treaty of 1963 which forbids atomic testing in either the atmosphere, underwater or space. While it resulted in a great reduction in radioactive pollution of the atmosphere, the Limited Test Ban did not halt the arms race; nuclear testing merely went underground after 1963. Two bilateral treaties signed by the United States and the Soviet Union became effective in 1976. The Th...

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Comments on 'P-wave amplitudes in the United States: east--west variations and variability', by Rhett Butler

Cited by 3 publications

References 10 publications

P-wave amplitude variation between the eastern and western United States: reply to Z. A. Der

P-wave amplitude variation between the eastern and western United States: reply to Z. A. Der

Structure of the Earth: Mantle and core

Underground nuclear explosions: Verifying limits on underground testing, yield estimates, and public policy

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