By recording microtremors simultaneously using arrays having two apertures, the effect of incoherent noise, which can act to depress coherency values, may be reduced, leading to better estimates of azimuthally-averaged coherency, and hence to improved shear-wave velocity profiles at sites. The method is exemplified by the use of 30 m and 40 m triangular arrays at McEwan Park, Lower Hutt, New Zealand, where the method is shown to result in better fits to theoretical coherency. Adequate

more »

... is confined to low frequencies (less than 4.5 Hz in this case). Estimates of Vs are modified for greater depths (50 to 200m in this example) but unaltered for near-surface materials.