'The threat continues': Meteorologist explains tsunami formation following earthquakes in Japan

EXPLAINER: How tsunamis are formed CNN Meteorologist Derek Van Dam explains how tsunamis may form after the 7.5 magnitude earthquake that shook Japan.

Japan issued its highest-level tsunami alert on Monday after a series of earthquakes rocked the country's west coast.

The Japan Meteorological Agency reported more than a dozen quakes in the Japan Sea off the coast of Ishikawa and nearby prefectures. The largest quake reached a magnitude of 7.6, collapsing buildings on Japan's main island, Honshu. The number of deaths and injuries remains unclear.

CNN meteorologist Derek Van Dam explained how tsunamis are likely to form following shifts in tectonic plates near the west coast of Japan.

"Tsunamis are not just one initial wave," he said in a CNN report on Monday. "They are a series of waves and sometimes the timing between the crest of the waves – that is, from wave height to wave height – could happen between five minutes to upwards of an hour or even longer. So the threat continues for the west coast of Japan."

He added that the threat of tsunamis also applies to portions of Russia and the Korean Peninsula.

Van Dam explained that the observed tsunami height detected so far is 1.2 metres in Wajima, Japan. The projections of how high these waves could become, he says, is all based on local topography.

"A tsunami wave is not equal in height," he said. "It's all dependent on the seabed and across the bathymetry across the shoreline, how the wave plays out. But the bottom line is that the tectonic plates have shifted near the west coast of Japan and that caused a displacement in the ocean's water, and that has allowed for the tsunami wave to occur."

With files from CNN