Himalayan earthquakes Kashmir Seismic Gap
Great earthquakes in the Himalaya have occurred repeatedly in the past and will continue to do so in the future. We do not know precisely when and where they will occur although in several locations we can calculate how much elastic energy is currently stored ready to drive a future earthquake. The map shows graphically how large these future earthquake in the Himalaya might be should a great earthquake occur today. The 2005 Mw7.6 Kashmir earthquake occurred 5 months after this figure was published at the extreme western end of the region. The westernmost M8 event, is a repeat of one inferred to have occurred in 1555 in SE Kashmir. Measurements show a slip deficit of 5 m to exist there now but its future rupture area is imperfectly known.
Deformation Sensors
GPS geodesy is accurate to roughly 1 mm, but strain-meters, tilt-meters and creepmeters effectively monitor signals that are much smaller. The tiltmeter (left) in Pozzuoli Italy measures relative vertical motions over a distance of 300 m with a precision of 0.1 microns, one ten-thousandth of the precision of GPS. Three biaxial tiltmeters operate near Seattle and one monitors inflation of the Long Valley caldera, California. Creep-meters on the San Andreas and Hayward faults monitor motions of the fault each minute to a precision of 10 microns.
principle of a creepmeter
tiltmeter operation.