Auxiliary material for Paper 2012GL054978R

Fan-Chi Lin, Victor C. Tsai, Brandon Schmandt, Zacharie Duputel, & Zhongwen Zhan

Seismological Laboratory, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA. (linf@caltech.edu)



Introduction

This auxiliary material contains four figures.
 
1. Fig. S1. Same as Fig. 2b but using 10-km distance bins. An air wave propagating near the sound speed (~320 m/s) is observed.

2. Fig. S2. Daily stacked cross-correlations for the month of August 2010. For each day, all available cross-correlations with distances between 1000 and 1050 km are stacked and bandpassed between 20 and 50-sec period. Days with earthquakes larger than 6.3 Mw in the CMT catalog are highlighted in red, and earthquake information is listed. Note the correlation between days with high core-phase amplitudes and large earthquakes. The high core-phase amplitudes on 8/5 (highlighted in blue) are likely due to the Mw 6.9 earthquake near the island of New Britain in Papua New Guinea late on 8/4. The 2-hour time difference between the earthquake and the onset of the 8/5 time series used in the cross-correlation suggests that the observed core phases originate from long-lasting body-wave coda excited by the earthquake.

 3. Fig S3. Stacked cross-correlations from August 12 for different back-azimuth directions. The location and the great circle path of the Ecuador earthquake on August 12 are shown at left (yellow circle and line). For each 20° back-azimuth bin, all available cross-correlations with distances between 1000 and 1050 km are stacked and bandpassed between 20 and 50-sec period. Note that we separate the positive and negative components of cross-correlations here such that the stacked cross-correlations reflect the energy coming from the different back-azimuth directions. The strong ScS phases observed between back azimuths of 120° and 180° suggest that the observed phases are due to ScS reverberations directly from the Ecuador earthquake. While strong PKIKP2 amplitudes for back azimuths between 300° and 360° may be due to direct phases emitted by the earthquake, the observed PKIKP2 phases for back azimuths between 40° and 140° are likely due to scattering and the wide Fresnel zone of the phase.

4. Fig. S4. Same as Fig. 2b but bandpassed between 5 and 10-sec period. Both PcP and PKIKP2 can be observed.