Locating Source Regions of Short-Period Secondary Microseisms

Primary and secondary microseisms are both generated by ocean wave interactions. It has been observed that, in some regions, the secondary microseism splits into long- and short-period bands. Short-period secondary microseism (SPSM) sources have traditionally been associated with nearby coastal segments, local storms or wave heights, and relatively constant offshore distances. However, the parameters controlling this split, as well as the precise spatial distribution of SPSM sources, remain poorly understood.

Motivated by the observation of a frequency bimodality in seismic noise cross-correlations in NE Iberia, we find evidence that the secondary microseism split occurs more broadly across the Mediterranean region. Using a combination of complementary and independent approaches, such as polarization analysis, source mechanism modeling, and attenuation assessment, we investigate possible variations in the location of source regions within the microseismic band. As a result, distinct source regions are consistently identified across all the methodologies employed, providing insight into the microseismic sources.

We further demonstrate that SPSM sources are well constrained, spatially localized, and highly dynamic. In this study, we reveal key variables directly related to the generation of SPSM sources, enhancing our understanding of the parameters controlling their spatial distribution. These findings are likely applicable to other regions with similar conditions.