@hypocentre
@Earthquakeguy
@DrLucyJones (The most common answer)
@earthquakesSF
@LastQuake
@geophysichick
@NatsSeismology
@ultraplinian
@Simoncarn
@janinekrippner
@lava_ice
@Volcanologist
@BGSvolcanology
@subglacial
@kaylai
@USGSVolcanoes
@geophysichick
@simoncarn
@volcanodoc (the recent notoriety might have helped)