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Sediment samples from the Bulgarian Exclusive Economic Zone (BEEZ) of the Black Sea rarely show indirect evidences for mud volcanoes existence - mud breccia. The analysis of seismicity in the area and studied mud volcanoes in the Black Sea allows the formulation of important hypotheses for a future study: * The Black Sea mud volcanoes are at older stage of their evolution - they are not erupted during the last century but their necks are still main pathways for deep strata degasation. The eruption process is too slow - let name it "snail eruption", and thus is invisible for onshore seismic stations. * Hypothetical mud volcanoes in the area of Bulgarian offshore obey to the same general rule of distribution according seismicity as known in the Black Sea (30 objects), as well as some other rules, determined by the sedimentation rate. [ABSTRACT FROM AUTHOR]

In the continental slope of Bulgarian Exclusive Economic Zone (BEEZ) of the Black Sea, where large volumes of gas hydrates (GH) could be concentrated in sediments near the seafloor, bottom water temperature varies periodically. This for example is due to seasonal changes or can be affected by aperiodic factors. The process of heat transfer from seawater to bottom sediments and thus on gas hydrate and slope stability is modeled. The results of modeling indicate that long time (50 years), seasonal and short-term variations of bottom water temperature may affect gas hydrate stability only in the upper 1-2 m of sediments. However, the zone where repetitive gas hydrate formation and decomposition occur because of bottom water temperature change is extensive in the area with water depths range 300-500 m mainly and up to 1000 m. Examples are shown from new seismic records received in 2011 from the consortium of scientists from all Black Sea countries in the frame of the project BLACK SEA SPAN. [ABSTRACT FROM AUTHOR]