GTSM in the Pacific North West of NSF'S PBO

 

Preliminary Data

 

 

AUGUST SEPTEMBER 2005

The expected Cascadia event beginning late in August 2005 was observed at P403 and Hoko (B004) sites, seeGoogle MAP of sites to September 30, propagating through P403 in late August, and a second cycle arriving at the HOKO strainmeter site around September 9, the total duration recorded to September 15 being about 18 days.

 

 

 

 

JUNE 2005

An early start to a new era of PBO/GTSM borehole strain meters.

With the grout only five hours old we had our first event in Northern California, the M7.2 of 02:50:54 on June 15, 2005, located 140 km west south west of Cresent City.

The data shown is the standard 20 Hz output of the GTSM system. Obviously the data are recorded through very incompletely set grout with very low modulus. The figures are raw single component data with a nominal calibration of 0.1 nanostrain per count. Peak amplitudes are about 30 nanostrain.

The upper figure shows the first arrival on a 10 minute time scale. The lower figure shows the next ten minutes of the event as seen at HOKO. The three channels show are at azimuths 120 degrees apart. The record is equally interesting on the fourth channel.