Hurricanes and tornadoes have seasons, but do earthquakes? They do in the Himalayas, and it’s during the winter. For years, seismologists had observed that far more earthquakes shook the massive Asian mountain range in the winter months than in the summer, but they couldn’t pinpoint the cause of this seasonal change. A new study of GPS and satellite data presented last month at a meeting of the American Geophysical Union has connected the increase in earthquake activity to the monsoon season that drenches the region each summer. When it rains, it shakes The Himalayas are a highly quake-prone region because of the stresses building up between the Indian and Eurasian plates as India continues to drive into Asia. Philippe Avouac of Caltech and his colleagues analyzed a catalog of 10,000 Himalayan quakes and found there were twice as many during the winter months (December to February) as during the summer. For example, for magnitude-3 quakes, there were up to 150 per month in the winter, but only 75 in the summer. (Quakes this small are often not even felt.) For magnitude-4 temblors (sometimes felt), the winter average was 16 per month, while the summer rate […]