Combined inversion for the three-dimensional Q structure and source parameters using microearthquake spectra
- Univ. of Colorado, Boulder (United States)
The estimation of Q values and/or source corner frequencies f{sub c} from single-station narrow-band recordings of microearthquake spectra is a strongly nonunique problem. This is due to the fact that the spectra can be equally well fitted with low-Q/high-f{sub c} or a high-Q/low f{sub c} spectral models. Here, a method is proposed to constrain this ambiguity by inverting a set of microearthquake spectra for a three-dimensional Q model structure and model source parameters seismic moment (M{sub o}) and corner frequency (f{sub c}) simultaneously. The inversion of whole path Q can be stated as a linear problem in the attenuation operator l* and solved using a tomographic reconstruction of the three-dimensional Q structure. This Q structure is then used as a geometrical constraint for a nonlinear Marquardt-Levenberg inversion of M{sub o} and f{sub c} and a new Q value. The method has been tested on a set of approximately 2,800 P wave spectra from the recordings of 635 microearthquakes from the Kaoiki seismic zone in Hawaii which were recorded at up to six stations. The hypocenters are distributed within a volume of approximately 18 {times} 18 {times} 15 km (depth). The Q model uncertainties have been estimated on the basis of several different tests: Self-consistency, constraining the corner frequencies, and additionally splitting the data set. The standard deviation of the final Q model which used a grid size of 1.5 {times} 1.5 {times} 2.0 km (depth) was less than 3% for the depth range 0-5 km, less than 5% between 5 and 7 km, and 7% between 7 and 9 km. For the given data set and depths below 3-5 km, the method is believed to be able to resolve the model dependent attenuation structure on a scale down to 1-2 km with a resolution of a few percent.
- OSTI ID:
- 5014136
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 95:B8; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
Similar Records
Preliminary results of microearthquake survey, Northern Adak Island, Alaska
The Use of Microearthquakes in Prospecting for Geothermal Areas and Magma Chambers
Related Subjects
MICROEARTHQUAKES
DATA ANALYSIS
CALCULATION METHODS
DATA PROCESSING
DEPTH
GEOLOGIC STRUCTURES
GEOMORPHOLOGY
HAWAII
HYPOCENTERS
MATHEMATICAL MODELS
PERFORMANCE TESTING
RESOLUTION
SEISMIC SOURCES
SEISMIC WAVES
THREE-DIMENSIONAL CALCULATIONS
WAVE PROPAGATION
DEVELOPED COUNTRIES
DIMENSIONS
EARTHQUAKES
FEDERAL REGION IX
GEOLOGY
NORTH AMERICA
PROCESSING
SEISMIC EVENTS
TESTING
USA
580000* - Geosciences