Synthetic study on SS waveform splitting and complication

Abstract

Some influential factors on the complication of SS waveform (with epicentral distance within 40°∼180°) are analyzed quantitatively by calculating the full-wave synthetic seismogram using propagation matrix method. Our results show that the transmission-conversion and reflection-conversion phases of S wave at the interface of Moho and free surface beneath bounce points are mainly responsible for the complication of SS waveform, the velocity contrast between the two sides of Moho boundary under SS bounce point also has great effects on the amplitudes of all the conversion and the reverberation phases; the properties of the crust at seismic station also play a role in the complication of SS waveform while the crustal thickness beneath bounce point is thinner relatively. At the same time, two sets of real SS waveform data at the two positions in eastern and western China are analyzed, and the splitting time between SS transverse component and radial component is measured by cross-correlation. Our analysis demonstrates that there is a positive correlation between crustal thickness and the splitting time because of the influences of adjacent conversion and reverberation phases, the splitting time in west with thick crust is obviously greater than that in the east with thin crust. Moreover, It is promising that one new method of measurement of crustal thickness will be developed by using the observed SS splitting time.

Seismic Anisotropy in the Java‐Banda and Philippine Subduction Zones and its Implications for the Mantle Flow System Beneath the Sunda Plate

“…However, these leave the asthenospheric flow undetected. SS wave splitting has been used to constrain anisotropic behaviors beneath SS bounce points in the upper mantle (Wolfe & Silver, ), but SS waveforms appear to be disturbed by crustal reverberations beneath SS bounce points (He et al, ; Rychert & Shearer, ). Phase pairs like S‐SS , S‐sS , ScS‐sScS , and ScS‐ScSScS have been used to isolate the upper mantle anisotropy beneath surface bounce points by removing the contributions from anisotropy in the upper mantle beneath stations and sources (e.g., Farra & Vinnik, ; Fischer & Yang, ; Vinnik & Farra, ; Yang & Fischer, ), but source, bounce point, and receiver splitting should be carefully considered in a proper order (Wolfe & Silver, ).…”

Refinement of Different Frequency Bands of Geomagnetic Vertical Intensity Polarization Anomalies before M > 5.5 Earthquakes

“…Observations and analyses have shown that when the signal originates from the high-altitude ionosphere (magnetosphere), the ULF magnetic field polarization value Y zh is usually less than 1, whereas the ULF magnetic field polarization value Y zh from seismogenic regions is ≥1; therefore, the polarization value is considered the key to differentiating between geomagnetic radiation originating from the ionosphere (magnetosphere) and seismic magnetic radiation originating from subsurface rocks (e.g., [18,[33][34][35]). In addition, precursory anomalies are usually indicated by high vertical intensity polarization ratio values (Y zh ≥ 1), while the postearthquake effects of geomagnetic observations are usually distinguished by the reduction in (recovery of) the vertical intensity polarization ratio to a normal range (Y zh < 1).…”

Structurally Preserved Liquidambar Infructescences, Associated Pollen, and Leaves from the Late Oligocene of the Nanning Basin, South China

“…Previously, fragmentary trilobate leaves with basal actinodromous venation and regularly spaced marginal teeth assigned to Liquidambar sp. were reported from the Eocene of China [ 51 , 52 ]. Recently, three Liquidambar species, L. maomingensis [ 30 ], L. bella N. Maslova et Kodrul [ 31 ], and L. hainanensis [ 32 ], were described from the Eocene of South China.…”

“…Furthermore, co-occurrences of Liquidambar leaves and reproductive structures are of considerable interest [ 18 , 22 , 30 , 32 , 33 , 50 ]. In China, altingioid megafossils are known from the Eocene [ 30 , 31 , 32 , 51 , 52 , 53 ], Miocene [ 7 , 28 , 33 , 50 , 54 ], and Upper Pleistocene [ 54 ]. Until now, megafossils of Liquidambar from the Oligocene of China have not been reported.…”