Abstract
The question of the reliability of GPS measurement as an index for
intraplate seismicity is raised here. Geodetic measurement of slip rate
along the Longmenshan Fault -a thrust structure that straddles the
border of the Indo-Australian Plate and Eurasian Plate produced gures
as low as 3mm/year, despite this low return, the magnitude 7.9 Wenchuan
earthquake occurred along this fault. Similar pattern was discovered in
both the New Madrid, South Carolina and Wabash seismic zones, where
geodetic derived strain rates of less than 2mm/yr fail to account for
the recurrence of magnitude 7 earthquakes every 500 years. Other
intraplate settings like Europe, Australia, South Africa showed similar
results, hence leading us to question how reliable a tool geodetic
measurement is in predicting the likelihood of earthquakes occurring in
the future. I conclude that seismic hazard assessment of intraplate
earthquakes based solely on geodetic strain rate measurement and the
location of occurrence of past (historic) earthquakes is spatially
limited and could be misleading, this is because where strain release
occurred (as past earthquakes) does not necessarily have to be the exact
location where strain accrual for future earthquakes take place, as
evidenced by the inability of the GPS strain rate to resolve seismic
moment release in all of the seismic zones in Central-Eastern United
States . Strain release in the future might occur on a distant
unidentified fault through transient stress perturbation -one that might
have been erroneously classified as ‘safe’ based on near-zero strain
rate picked up by today‘s GPS measurements.