Rayleigh and Love Wave Dispersion Curves from Seismic Noise of the North African and South Iberian Peninsula Lithospheric Structure and Collision Zone

American Geophysical Union Fall Meeting, 12-16 December 2022, ChicagoCurrently, there is uncertainty about the structure, evolution, and geodynamics of the North African and South Iberian Peninsula lithospheric structure and collision zone. Models of the lithosphere of the region coincide in some anomaly zones, such as the subduction slab under the Gibraltar arc. However, they show discrepancies in distribution and polarity of the velocity anomalies in the onshore and offshore of most of North Africa. To contribute to the study of the lithospheric structure and to unveil the tectonics in this controversial region, ambient noise Rayleigh and Love surface wave dispersion curves are computed from temporary and permanent broadband stations located in the Iberian Peninsula, North Africa, and Atlantic islands (Madeira, Canarias, Balearic Islands). The methodology employed contemplates the seismic interferometry of 14 months ambient noise records using phase cross-correlation and the subsequent stacking of the cross-correlograms to obtain the Empirical Green's Function (EGF), and finally, the implementation of the Frequency-Time Analysis (FTAN) to measure the dispersion characteristics of surface wave EGFs present in the ambient noise. The distribution of the almost 100 broadband stations in North Africa, Portugal, Spain, and the Atlantic islands, results in a broad path coverage in the North African and South Iberian Peninsula lithospheric structure and collision zone, complementing the previous Rayleigh wave velocity models. Furthermore, current studies in this region are Rayleigh-waves based, so the Love-wave dispersion curves calculated from this study yield new information on the media velocity anisotropyPeer reviewe

Seasonal trends and population status of the highly threatened Pteropus livingstonii in the Comoros archipelago

Abstract Flying foxes of the genus Pteropus, especially those inhabiting islands, face increasing pressure from anthropogenic threats. A first step to implementing effective conservation actions is to establish monitoring projects to understand a species’ population status and trend. Pteropus species are highly affected by seasonality which further requires regular, repeated, and long-term data to understand population trends, and reactions to severe weather events. In the present case study, a regular, bi-annual population census was implemented on Comoros between 2016 and 2023 for the highly threatened Livingstone’s fruit bat, Pteropus livingstonii, and compared the results of standardized monitoring to historical population data. Seasonality had a large impact on the number of bats found at roost sites, with more bats present in the wet season, but the data over the past eight years revealed no significant in- or decrease in the number of bats counted on the island Anjouan. We estimated around 1,200–1,500 bats on Anjouan and 300–400 bats on Mohéli, and found that landcover type has no measurable effect on population distribution at roost sites. Our study highlights the need for long-term surveys to understand past population trends and that single counts are not sufficient to draw final conclusions of a species’ status