Double-frequency microseisms in ambient noise recorded in Mississippi

This research presents the power spectral density (PSD) of double-frequency (DF) microseisms of 13 continuous single-point long-term ambient noise recordings (LTRs) at five inland and two coastal locations selected in Mississippi and Louisiana states and 234 single-point short-term ambient noise recordings (STRs) in northern Mississippi. By correlating PSD of LTRs with the simultaneous ocean data (including significant ocean wave frequency, significant ocean wave height, ocean wind speed, and above-ocean atmosphere pressure) of the Atlantic Ocean and Gulf of Mexico, as well as local atmosphere pressure and wind speed, DF microseisms observed in northern Mississippi were shown to be shaped by a combined impact of both wave climates of the Atlantic Ocean and Gulf of Mexico. Particle motion analysis and calculation of vibration angle defined separately for LTRs and STRs strengthen this conclusion. The DF and PSD level at DF of STR plots in the horizontal direction versus unconsolidated sediment thickness show significant differences from the plots in the vertical direction, which indicates that the shear-wave resonance in thick sediments modifies the DF microseisms more obviously in the horizontal than in the vertical direction.