A seismograph on the Danish island of Bornholm twice recorded spikes representing earth tremors on Monday, the day on which the Nord Stream 1 and 2 gas pipelines underwent dramatic falls in pressure, German geological research centre GFZ said.
The seismograph recorded near-silence until 0003 GMT (2am local time) when there was a spike representing a tremor in the earth followed by a continuous hissing waveform. The pattern repeated itself at 1700.
