  The seismic events that preceded the leaks in the Nordstream pipelines in the
Baltic Sea have been interpreted as explosions on the seabed, most likely
man-made. We use a polarization-based location method initially developed for
marsquakes to locate the source region without a subsurface velocity model. We
show that the 2 largest seismic events can be unambiguously attributed to the
methane plumes observed on the sea surface. The two largest events can be
located with this method, using 4 and 5 stations located around the source,
with location uncertainties of 30km and 10x60km. We can further show that both
events emitted seismic energy for at least ten minutes after the initial
explosion, indicative of resonances in the water column or the depressurizing
pipeline.
