Seasonal Modulation of Interseismic Strain Buildup in Northeastern Japan Driven by Snow Loads
Kosuke Heki
Distinct periodic variations with annual frequencies are often
found in the time series of continuous Global Positioning System (GPS)
site coordinates in northeastern Japan. They show maximum arc-normal
contraction of a few millimeters as well as maximum subsidence of 1 to
2 centimeters, both in March. In northeastern Japan, it snows heavily
on the western flank of the backbone range, attaining a maximum depth
of several meters in March. When observed snow depths were compared
with the load distribution estimated from the GPS data, the surface
loads caused by the snow were found to be largely responsible for the
annual displacement of GPS sites. The snow load modulates secular
strain buildup in northeastern Japan due to the Pacific Plate
subduction, but its relevance to the seasonal change of earthquake
occurrences remains uncertain.
Division of Earth Rotation, National Astronomical Observatory,
2-12 Hoshigaoka, Mizusawa, Iwate 023-0861, Japan. E-mail:
heki{at}miz.nao.ac.jp
