--> --> Description and Interpretation of the 1927 Earthquakes and Catastrophic Methane Outbursts Offshore Crimea, Northern Black Sea, by Soviet Geoscientists

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Description and Interpretation of the 1927 Earthquakes and Catastrophic Methane Outbursts Offshore Crimea, Northern Black Sea, by Soviet Geoscientists

Abstract

Prof. P.A.N. Dvoychenko provided an exceptional account of the earthquakes, associated methane outbursts and renewed mud volcanism in the Crimea occurring during the summer and autumn of 1927. In his paper published in the Soviet equivalent of “Nature” magazine in 1928, he described in details the inception of earthquake activity on June 26th, 1927, which took all the holidaymakers enjoying the Crimean Riviera by surprise. Besides providing description of the damage caused by the earthquake and the aftershocks, this paper is a key account of the numerous sightings of spectacular offshore flames and large fires not seen since then. During the early hours of September 12th 1927 very large flames were seen from the coastline on the horizon from different parts of Crimea, such as Sevastopol, Cape Lucullus and Yalta. The duration of these “pale” flames above the sea surface was anywhere between 1–2 minutes and they were huge according to the eyewitness accounts, i.e. 500(!) m high and 2,000 m in width. The pale color of these gigantic flames was compared to the glow of phosphane. A different set of offshore flames were observed from Sudak and Yalta the same night. These started out in whitish color and became very bright red colored, burning for more than an hour locally. Sometimes large bright flashes, which even lit up the sky, were accompanied by sound of explosions. These explosions and large fires were interpreted as exploding and burning hydrocarbon gases following their ignition by phosphane. All these gases were released from the seabed along fault zones as the result of repeated earthquake activity. An alternative interpretation today could be that some of the early flames were “earthquake lights”. However, there is a very large segment of the NW Black Sea where thousands of gas flares were documented in the last few years, mostly in the area of the Paleo-Dnepr delta area, to the W and SW of Crimea. Biogenic gas trapped in Cenozoic sediments is an important play type in the Black Sea as methane is produced in the Galata Field offshore Bulgaria and in the Akcakoca Field offshore Turkey. Therefore the interpretation of the huge flames, fires and explosions observed offshore Crimea in 1927 in terms of combusted methane derived from the bottom of the Black Sea is not only a unique story in the history of petroleum geology but it also has important implications for exploration efforts offshore Ukraine.