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Time-Space Distribution of Coda Q in Fault Zones and Surface Wave Dispersion in Eastern China (Earthquakes; Hawaii; Aleutians).

紀錄類型:	書目-語言資料,手稿 : Monograph/item
正題名/作者:	Time-Space Distribution of Coda Q in Fault Zones and Surface Wave Dispersion in Eastern China (Earthquakes; Hawaii; Aleutians)./
作者:	Huang, Zhongxian.
面頁冊數:	1 online resource (165 pages)
附註:	Source: Dissertations Abstracts International, Volume: 48-07, Section: B.
Contained By:	Dissertations Abstracts International48-07B.
標題:	Geophysics. -
電子資源:	click for full text (PQDT)
ISBN:	9798206124972

Time-Space Distribution of Coda Q in Fault Zones and Surface Wave Dispersion in Eastern China (Earthquakes; Hawaii; Aleutians).
Huang, Zhongxian.

Time-Space Distribution of Coda Q in Fault Zones and Surface Wave Dispersion in Eastern China (Earthquakes; Hawaii; Aleutians). - 1 online resource (165 pages)

Source: Dissertations Abstracts International, Volume: 48-07, Section: B.

Thesis (Ph.D.)--University of Colorado at Boulder, 1987.

Includes bibliographical references

Coda-Q were studied to search for temporal and spatial variations related to the November 16, 1983 Hawaii earthquake (Ms6.6) and the May 7, 1986 Aleutian earthquake (Ms7.7). More than 300 microearthquakes in each case, recorded by local networks, were used. The Q values were calculated from the coda decay rate using Aki's single back-scattering model. One-year average Q values were stable within the ±10% range for six years before the Hawaii earthquake and for five years before the Aleutian earthquake. No precursory change was detected in either case. After the 1986 Aleutian earthquakes, coda-Q decreased about 10% in the aftershock zone. In both cases the coda-Q showed spatial variations in the pre-mainshock stage. In the Hawaiian case, the region northwest of the mainshock epicenter yielded an average Q about 15% higher than that of the southeast region. The lower-Q region also showed higher seismicity and higher b-value, suggesting that the lower Q is due to a more fractured crust in that region. In the Aleutian case, the coda-Q within the mainshock rupture zone was about 20% higher than in the region to the west. The Q difference may be related to a difference in stress levels within and outside the rupture zone. Our study shows the difficulty in using coda-Q for earthquake prediction. The early part of the coda is so sensitive to the path and source effects that the random fluctuation of the measurements is relatively large compared to the possible precursory change. The later part of the coda is insensitive to Q changes in a small volume. The long-period recordings from three WWSSN stations were used to derive the Love and Rayleigh wave group velocity dispersion curves along paths which cross eastern China. The inverted velocity structures indicate a low shear velocity in the upper mantle in comparison to stable continental areas. The structure of the South China Block is relatively uniform. The North China Block, which is tectonically more active, is laterally more heterogeneous. In the coastal region, a north-northeast trending discontinuity in the crustal structure is inferred from the non-great-circle propagation paths.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2024

Mode of access: World Wide Web

ISBN: 9798206124972Subjects--Topical Terms:

686174
Geophysics.
Index Terms--Genre/Form:

554714
Electronic books.

Time-Space Distribution of Coda Q in Fault Zones and Surface Wave Dispersion in Eastern China (Earthquakes; Hawaii; Aleutians).
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245 1 0 $a Time-Space Distribution of Coda Q in Fault Zones and Surface Wave Dispersion in Eastern China (Earthquakes; Hawaii; Aleutians).
264 0 $c 1987
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500 $a Source: Dissertations Abstracts International, Volume: 48-07, Section: B.
500 $a Publisher info.: Dissertation/Thesis.
502 $a Thesis (Ph.D.)--University of Colorado at Boulder, 1987.
504 $a Includes bibliographical references
520 $a Coda-Q were studied to search for temporal and spatial variations related to the November 16, 1983 Hawaii earthquake (Ms6.6) and the May 7, 1986 Aleutian earthquake (Ms7.7). More than 300 microearthquakes in each case, recorded by local networks, were used. The Q values were calculated from the coda decay rate using Aki's single back-scattering model. One-year average Q values were stable within the ±10% range for six years before the Hawaii earthquake and for five years before the Aleutian earthquake. No precursory change was detected in either case. After the 1986 Aleutian earthquakes, coda-Q decreased about 10% in the aftershock zone. In both cases the coda-Q showed spatial variations in the pre-mainshock stage. In the Hawaiian case, the region northwest of the mainshock epicenter yielded an average Q about 15% higher than that of the southeast region. The lower-Q region also showed higher seismicity and higher b-value, suggesting that the lower Q is due to a more fractured crust in that region. In the Aleutian case, the coda-Q within the mainshock rupture zone was about 20% higher than in the region to the west. The Q difference may be related to a difference in stress levels within and outside the rupture zone. Our study shows the difficulty in using coda-Q for earthquake prediction. The early part of the coda is so sensitive to the path and source effects that the random fluctuation of the measurements is relatively large compared to the possible precursory change. The later part of the coda is insensitive to Q changes in a small volume. The long-period recordings from three WWSSN stations were used to derive the Love and Rayleigh wave group velocity dispersion curves along paths which cross eastern China. The inverted velocity structures indicate a low shear velocity in the upper mantle in comparison to stable continental areas. The structure of the South China Block is relatively uniform. The North China Block, which is tectonically more active, is laterally more heterogeneous. In the coastal region, a north-northeast trending discontinuity in the crustal structure is inferred from the non-great-circle propagation paths.
533 $a Electronic reproduction. $b Ann Arbor, Mich. : $c ProQuest, $d 2024
538 $a Mode of access: World Wide Web
650 4 $a Geophysics. $3 686174
655 7 $a Electronic books. $2 local $3 554714
690 $a 0373
690 $a 0467
710 2 $a University of Colorado at Boulder. $3 1191314
710 2 $a ProQuest Information and Learning Co. $3 1178819
773 0 $t Dissertations Abstracts International $g 48-07B.
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=8723469 $z click for full text (PQDT)