Q Models for Lg Wave Attenuation in the Central United States

dc.contributor.authorConn, Arielen
dc.contributor.committeechairChapman, Martin C.en
dc.contributor.committeememberMartin, James R.en
dc.contributor.committeememberHole, John A.en
dc.contributor.departmentGeosciencesen
dc.date.accessioned2013-04-12T08:00:21Zen
dc.date.available2013-04-12T08:00:21Zen
dc.date.issued2013-03-22en
dc.description.abstractA series of small- to moderate-sized earthquakes occurred in Arkansas, Oklahoma and Texas from 2010 to 2012, coinciding with the arrival of the EarthScope Transportable Array (TA). The data the TA recorded from those earthquakes provide a unique opportunity to study attenuation of the Lg phase in the mid-continent and Gulf Coastal region. The TA data reveal previously unrecognized regional variability of ground motion propagation in the central United States. A study of the Fourier amplitude spectra shows the Lg phase exhibiting strong attenuation for ray paths from Arkansas, southwest through the Ouachita Orogenic Belt and into central Texas, and south into the Gulf Coastal region. Less attenuation is seen in central Texas for ray paths extending directly south from Oklahoma, though attenuation remains strong along the Gulf Coast. In contrast, ray paths to the north, regardless of source location, exhibit very little attenuation, especially in northern Missouri and southern Iowa. Regression models that incorporate near-receiver (distance-independent) attenuation due to thick sediments in the Gulf Coastal Plain successfully reduce path-related bias in the regression residuals for stations near the Gulf Coast. Dividing the central United States into three regions (the Gulf Coastal Plain, the Great Plains and the Midwest) further reduced bias, and allowed for the development of Q models in the Gulf Coastal Plain and the Great Plains. In the Gulf Coastal Plain, the Q model for that part of the ray path through the basement, from the earthquake to the base of the sediment deposits below the receiver, was found to be Q=(295±11)*f^(0.645±0.029). The model for attenuation in the sediment section near the receiver in the Gulf Coastal Plain is Q=(72±6.7)*f^(0.32±0.06) (velocity through the sediments is unconfirmed but thought to be approximately 1 km/s). The Q model for the Great Plains is  Q=(692±61.3)*f^(0.43±0.07). The Midwest region exhibited extremely complicated behavior: the data indicate little or no attenuation of amplitudes in the frequency band from approximately 0.7 to 2.0 Hz. As a consequence, Q in the Midwest region in that frequency range could not be realistically determined.en
dc.description.degreeMaster of Scienceen
dc.format.mediumETDen
dc.identifier.othervt_gsexam:385en
dc.identifier.urihttp://hdl.handle.net/10919/19317en
dc.publisherVirginia Techen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectLg wave attenuationen
dc.subjectQ valueen
dc.subjectearthquake wave propagationen
dc.subjectCentral United Statesen
dc.subjectgeometrical spreadingen
dc.titleQ Models for Lg Wave Attenuation in the Central United Statesen
dc.typeThesisen
thesis.degree.disciplineGeosciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

Files

Original bundle
Now showing 1 - 2 of 2
Loading...
Thumbnail Image
Name:
Conn_A_T_2013.pdf
Size:
82.5 MB
Format:
Adobe Portable Document Format
Loading...
Thumbnail Image
Name:
Conn_A_T_2013_support_1.pdf
Size:
29.85 KB
Format:
Adobe Portable Document Format
Description:
Supporting documents

Collections