| We analyze 2 years of continuous ambient noise data recorded at 24 broadband stations around the San Jacinto Fault Zone (SJFZ), California. Using similar techniques as Roux et al. (2005), we obtain noise-based cross-correlations in the frequency range 0.1--1.3 Hz in +/-50 seconds time windows across >200 station pairs with distances ranging from 2 to 130 km. To study the effect of seasonally varying noise sources on the resulting cross-correlations, we stack 3-months of data from winter and summer periods separately. The following two main arrivals are resolved independent of the season: (1) a Rayleigh wave travelling at ∼3.2 km/s and (2) an arrival around t=0 likely resulting from teleseismic P-phase with near-vertical incidence. In addition, two phases travelling roughly at 6 km/s and 12 km/s appear during winter which are also attributed to teleseismic P-phases with high apparent velocities. Amplitudes in winter are stronger than in summer, reflecting the seasonally dependent energy content of noise in the microseisms frequency band. An approximate 3--6% velocity contrast across the SJFZ can be resolved from our analysis. |
