I. Attenuation Tomography. II. Modeling Regional Love Waves: Imperial Valley to Pasadena

摘要: Abstract to Part I The inverse problem of seismic wave attenuation is solved by an iterative back-projection method. quality factor, Q, can be estimated approximately inverting the S-to-P amplitude ratios. Effects various uncertain ties in method are tested and tomography shown useful solving for spatial variations structure estimating effective factor attenuating anomalies. Back-projection applied two cases southern California: Imperial Valley Coso-Indian Wells region. In region, a highly body (S-wave (Qβ ≈ 30) coincides with slow P-wave anomaly mapped Walck Clayton (1987). This coincidence suggests presence magmatic or hydrothermal 3 5 km deep Indian Valley, travel-time anomalies S-wave were found Brawley zone at depth 8 12 km. very low 20) velocity 10% slower than surrounding areas. These results suggest either intrusions, fractures depth, possibly related active shear zone. No-block inversion generalized tomographic utilizing continuous form problem. posed , no-block technique same data set used tomography. A relatively small little redundancy enables us apply both techniques similar degree resolution. obtained methods similar. By applying set, formal errors resolution directly computed final model, objectivity result enhanced. Both local earthquakes Kilauea, Hawaii, solve under Kilauea East Rift Zone. shallow magma chamber, Zone Mauna Loa chamber delineated as Detailed reveals secondary reservoirs Ulu Puu Oo, present sites volcanic eruptions. Hilina Fault attenuating, dominating depths. conduit system along summit shows up supply channel extending down 6 Southwest Zone, on other hand, not anomalies, except 8-12 km, where imaged west Kou. Ylauna seated deeper level (about 6-10 km) chamber. Resolution area good area, there trade-off between extent error that due poor ray coverage. well resolved, according test done location II Long period seismograms recorded Pasadena occurring profile studied terms source phenomena (e.g., mechanisms depths) versus path effects. Some events have known parameters, determined teleseismic near-field studies, master forward modeling exercise derive Green's functions (SH displacements pure strike-slip dip-slip mechanism) describe propagation effects profile. timing waveforms records matched synthetics calculated from 2-dimensional models. best section begins thin crust containing basin thickens towards Pasadena. detailed nature transition base controls early arriving shorter periods (strong motions), while edge scattered longer surface waves. From waveform characteristics alone, easily distinguished events, amount motion also determined. Those rupturing sediments, such 1979 earthquake, recognized late-arriving Love has been delayed across valley structure.