Himalayan earthquakes:
Research materials for important events
In the past 50 years more than 94,000 people have been killed by building collapse and avalanches associated with Himalayan earthquakes. In the same time period,148 climbing related deaths have occurred climbing Mt. Everest, which is located some 20 km north of the epicenter of the great Bihar/Nepal earthquake of 1934.
Until recently it was believed that four magnitude 8 earthquakes had occurred in the past 100 years. The first of these events (1897) is now known not to have occurred in the Himalaya but beneath Shillong, the second (1905) has been recalculated to have been smaller (M=7.8) and were it to recur today would do so in a M=7.5 earthquake. The number of great earthquakes known in the past several centuries appears inadequate to accomodate the 16-18 mm/year of Himalayan convergence observed geodetically.We conclude that several M>8 earthquakes may be overdue (see moment deficit discussion). Due to increased populations and urbanization in the Ganges plain, the death toll from any one of these earthquakes could now exceed 1 million.
We know only approximately where, these future earthquakes will occur and we know considerably less about their timing. Geodetic data, when compared to historical earthquake data, suggest that sufficient slip is now available (>9 m) to drive a Magnitude 8 earthquake in some locations. The figure below shows the Himalaya "straightened " with the locations of rupture zones of large historical earthquakes in the past 500 years. Earlier ruptures are less certain as suggested by queries in the figure below. In no locations do we see clear evidence for a recurring great rupture and the recurrence interval is thus speculative. A consideration of the Himalaya and the Tibetan plateau as an integrated elastic system suggests that while recent earthquakes occur at roughly 500 year intervals, much larger earthquakes must occasionally occur to deplete accumulating reservoir of elastic energy in southern Tibet.
The Indian plate moves 5 cm closer to Asia each year (about 1 mm each week according to GPS measurements), and Tibet moves 32 mm closer to Asia each year. As a result the Kingdom of Nepal is shortened by 18 mm each year. This is equivalent to the loss of two soccer fields a year along its 600 km-long northern border. The mountains of Tibet, the Tien Shan and the Himalaya are the result of compression caused by plate collision.