An investigation of the regional variations and frequency dependence of anelastic attenuation in the mantle under the United States in the 0.5-4 Hz band

Der, Zoltan A.; McElfresh, T.W.; O’Donnell, Anne E.

doi:10.1111/j.1365-246x.1982.tb04936.x

Cited by 81 publications

(55 citation statements)

References 52 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, some work has been done on attenuation in the frequency range 1.0 to 8.0 Hz (DER et al, 1982;BACHE et al, 1986;BOWMAN, 1988) and higher (WALCK, 1988). Absolute values of upper-mantle attenuation from low frequency studies have traditionally been difficult to reconcile with those from high-frequency studies because most investigations comprise seismic waves with fundamentally different travel paths.…”

Section: Introductionmentioning

confidence: 99%

Attenuation of Broadband P and S Waves in Tonga: Observations of Frequency Dependent Q

Flanagan¹,

Wiens²

1998

Pure and Applied Geophysics

View full text Add to dashboard Cite

Teleseismic broadband recordings of intermediate and deep focus earthquakes are used to quantify both compression (Q h ) and shear (Q i ) wave attenuation within the Lau backarc basin. A spectral-ratio method is employed to measure differential attenuation (lt*) between the depth phases sS, pP, and sP and the direct S and P phases over the frequency band 0.05 and 0.5 Hz. We use a stacking algorithm to combine the spectra of several phase pairs from a single event, having similar azimuth and range, to obtain more robust lt* measurements; these estimates are then used to compute the average Q above the focal depth. Q i and Q h are measured directly from the sS-S and pP-P phase pairs respectively, however, the interpretation of lt* measured from sP-P requires assumptions about the ratio Q h /Q i . We find an empirical ratio of Q h /Q i =1.93 for this region and use it to compute Q h and Q i from the Q sP observations.We observe lateral and depth variations in both Q i and Q h beneath the tectonically active Lau Basin and the geologically older, inactive Lau Ridge and Fiji Plateau. The upper 200 km beneath the Central and Northern Lau Basin show a Q i of 45 -57 and a Q h of 102 -121, and Q appears to increase rapidly with depth. The upper 600 km beneath the Lau backarc basin has a Q i of 118 -138, while over the same depth interval we observe a higher Q i of 139 -161 beneath the Lau Ridge and Fiji Plateau. We also find Q h of 235-303 beneath the northern Lau Basin and a higher Q h of 292 -316 beneath the Fiji Plateau and the Lau Ridge measured directly from pP-P phase pairs. These geographic trends in the broadband Q measurements correlate with our previous long-period estimates of Q i in this region, however, the broadband measurements themselves are higher by about a factor of two. These observations suggest substantial frequency dependence of Q in the upper mantle, beginning at frequencies less than 1.0 Hz and consistent with the power-law form: Q8 h with h between −0.1 and −0.3.

show abstract

Section: Introductionmentioning

confidence: 99%

Attenuation of Broadband P and S Waves in Tonga: Observations of Frequency Dependent Q

Flanagan¹,

Wiens²

1998

Pure and Applied Geophysics

View full text Add to dashboard Cite

show abstract

“…The square of the velocity seismogram u and frequency-dependent attenuation correction t* are integrated over the angular frequency w. Represented in seconds, t* is the reciprocal of the characteristic w representing the frequency by which an exponential decay of energy is 1/e its original value [Der et al, 1982]. The values of t* used in this study were introduced by Choy and Boatwright [1995] and put in equation form by Newman and Okal [1998].…”

Section: Energy Calculationmentioning

confidence: 99%

Global evaluation of large earthquake energy from 1997 through mid-2010

Convers

Newman

2011

J. Geophys. Res.

View full text Add to dashboard Cite

[1] We develop an updated radiated seismic energy E catalog of global earthquakes with seismic moment M 0 ≥ 10 19 Nm (M W ≥ 6.7) from 1997 through mid-2010, recording 342 events using 17849 seismograms. Station-specific corrections and event duration-dependent total P wave group calculations allow for improved E determinations for large-and long-duration earthquakes. We find the global mean energy-to-moment ratio = log 10 (E/M 0 ) = −4.59 ± 0.36. Robust deviations are found for thrust ( T = −4.74), strike-slip ( SS = −4.44), and normal ( N = −4.51) faulting events. For two regions with recent energy deficient tsunami earthquakes (TsE), we examine all large thrust earthquakes with M 0 ≥ 5 × 10 17 Nm (M W ≥ 5.7), to identify a regional characterization in their relative radiated energy-to-moment ratio. While thrust events along Java, Indonesia, the site of two TsE events in 1994 and 2006, are comparable ( T−JV = −4.91) to the global thrust average, events along the Middle America Trench (MAT), the site of the 1992 Nicaragua TsE, are consistently deficient ( T−MAT = −5.15). Along the MAT, a trend of increased deficiency in radiated energy to the southeast occurs in the direction of more rapid plate convergence. Global thrust mechanisms become increasingly deficient in radiated seismic energy at shallow depths, with TsE events representing the shallowest and most energetically deficient end-member of the events in the study. Results suggest thrust events are highly variable but tend to increase in apparent stress from about 15 kPa near the surface to 2 MPa near 70 km depth.

show abstract

“…Individual measurements of path-specific Q, or tomographic inversions of laterally varying Q models, are typically published with discussions of the measurement error or uncertainty (e.g., MITCHELL, 1995;XIE et al, 2004;PHILLIPS et al, 2005;ROMANOWICZ and MITCHELL, 2007;PASYANOS et al, 2009). The vast Q measurements and tomographic Q models collectively reveal two main features of Q in the Earth's crust and mantle: it is highly laterally variable (by a factor of 10 as compared to the velocity variation which is typically less than 20-30%), and often frequency dependent (e.g., DER et al, 1986DER et al, , 1987ANDERSON, 1989;MITCHELL, 1991;XIE and MITCHELL, 1990;MITCHELL and XIE, 1994;WIENS 1994, 1998;SOBOLEV et al, 1996;XIE, 1998;XIE et al, 2004XIE et al, , 2006GUNG and ROMANOWICZ, 2004;SELBY and WOODHOUSE, 2002;WARREN and SHEARER, 2002;SHITO et al, 2004;PHILLIPS et al, 2005;DALTON and EKSTROM, 2006;LEKIC et al, 2009;PASYANOS et al, 2009, also see summaries by ANDERSON, 1989;FLANAGAN and WIENS, 1994;MITCHELL, 1995;ROMANOWICZ, 1998;ROMANOWICZ and MITCHELL, 2007;SATO and FEHLER, 2009). These features have led to inferences of variations of temperature and occurrence of melting in the crust and upper mantle, variations of pore fluid content and other forms of small-scale crustal structure heterogeneities.…”

Section: Introductionmentioning

confidence: 99%

Can We Improve Estimates of Seismological Q Using a New “Geometrical Spreading” Model?

Xie

2010

Pure Appl. Geophys.

View full text Add to dashboard Cite

Abstract-Precise measurements of seismological Q are difficult because we lack detailed knowledge on how the Earth's fine velocity structure affects the amplitude data. In a number of recent papers, Morozov (Geophys J Int 175:239-252, 2008; Seism Res Lett 80:5-7, 2009; Pure Appl Geophys, this volume, 2010) proposes a new procedure intended to improve Q determinations. The procedure relies on quantifying the structural effects using a new form of geometrical spreading (GS) model that has an exponentially decaying component with time, e -ct Ác is a free parameter and is measured together with Q. Morozov has refit many previously published sets of amplitude attenuation data. In general, the new Q estimates are much higher than previous estimates, and all of the previously estimated frequency-dependence values for Q disappear in the new estimates. In this paper I show that (1) the traditional modeling of seismic amplitudes is physically based, whereas the new model lacks a physical basis; (2) the method of measuring Q using the new model is effectively just a curve fitting procedure using a first-order Taylor series expansion; (3) previous highfrequency data that were fit by a power-law frequency dependence for Q are expected to be also fit by the first-order expansion in the limited frequency bands involved, because of the long tails of power-law functions; (4) recent laboratory measurements of intrinsic Q of mantle materials at seismic frequencies provide independent evidence that intrinsic Q is often frequency-dependent, which should lead to frequency-dependent total Q; (5) published long-period surface wave data that were used to derive several recent Q models inherently contradict the new GS model; and (6) previous modeling has already included a special case that is mathematically identical to the new GS model, but with physical assumptions and measured Q values that differ from those with the new GS model. Therefore, while individually the previous Q measurements have limited precision, they cannot be improved by using the new GS model. The large number of Q measurements by seismologists are sufficient to show that Q values in the Earth are highly laterally variable and are often frequency dependent.

show abstract

An investigation of the regional variations and frequency dependence of anelastic attenuation in the mantle under the United States in the 0.5-4 Hz band

Cited by 81 publications

References 52 publications

Attenuation of Broadband P and S Waves in Tonga: Observations of Frequency Dependent Q

Attenuation of Broadband P and S Waves in Tonga: Observations of Frequency Dependent Q

Global evaluation of large earthquake energy from 1997 through mid-2010

Can We Improve Estimates of Seismological Q Using a New “Geometrical Spreading” Model?

Contact Info

Product

Resources

About