stable levelling and locking methods applicable for borehole very broad band seismic sensors...
TRANSCRIPT
Stable levelling and locking methods applicable for borehole very broad band seismic sensors including tilt meters
presented at
SUPERSITES COORDINATION WORKSHOP Monday 10 June 2013
Cansun Guralp
Why borehole instruments?
- Reduce the seismic back ground noiseFacilitates to record seismic data under reduced noise conditions in the long period and short period seismic bands thereby improving:
• signal‐to‐noise ratio• magnitude detection threshold • precision of hypocentre determination
- Get closer to the source of earthquakesAllows to broaden the frequency band of the recorded seismic signals including high frequency components.- Provide multidisciplinary seismic observatory
• Strong motion• Broad band 360 second period to 200 Hz, with single jaw hole lock. • Two axis tilt meter with three jaw hole-lock • High resolution Temperature sensor• Strain gauge, cemented
• Deployment options for installation:– with a hole-lock
– Single arm hole lock with skids– Three jaw hole lock – or with bishops hat orientation system
– in SAND packed borehole, without a hole lock – Cemented sensor
– in a cased borehole– in an un-cased boreholeOther features:– Options such as Horizontal component orientation– provided with integrated accelerometer
CMG-3TB Seismometer
Bangladesh
Pakistan
Kazakhstan
Taiwan
China
Russia
Japan
South Korea
Australia
New Zealand
Turkmenistan
Oman
Saudi Arabia
Turkey
IranIsrael
Niger
Switzerland
Belgium
UK
Norway
Senegal
Tunisia
Montserrat
BrazilPeru
Mexico
USA
USA
Antarctica
CMG-3TB: example of some Global Installations
With three jaw hole-lock
CMG-3TB Seismometer
Borehole Sensor with three jaw hole lock
Some examples of borehole seismometer packages
Some examples of borehole seismometer packages
Borehole Sensor with three jaw hole lock
Joint experiment:3T/5T borehole sensor + DM24 at >1000 m depth,optical data transmissionto well head
Closer to source I
Our sensor deployed at1039.50 m in Pilot Hole
Closer to source II
Example of typical down-hole recording: Microearthquakes not observed on surface, most common type of microearthquake observed: S-P time: 0.74 sec hypocentral distance between 4-5 km
Earth Tides
some peculiarities to be resolved:1. ultra long period (4-8 min) noise
Pinnacle tiltmeter (2007)
CMG-3TB Case Studies Data from 4 different sensor installations at the same location, high
frequency performance of 3TB is clearly demonstrated
Presented at the IRIS Broad-Band Instrumentation Workshop; Lake Tahoe, Mar 24-26, 2004
• Titanium case with three component broad band sensor 360 sec to 50 Hz.
• ± 5 degrees of tilt compensation.• 4 Channel 24 bit digitiser with time
synchronisation.• Mass position outputs used as tilt data
and compared to a very high resolution tilt sensor 5*10-9 radian.
• Deployed with cement at 3000 meter depth. 2400 meters sea water and 600 meters of sea bottom borehole.
CMG-3TBD Seismometer
CMG-3TB Seismometer
- Reduce the seismic noiseFacilitates to record seismic data under reduced noise conditions in the long period and short period seismic bands thereby improving:
• signal‐to‐noise ratio• magnitude detection threshold • precision of hypocentre determination
- Get closer to the source of earthquakesAllows to broaden the frequency band of the recorded seismic signals including high frequency components.- Provide multidisciplinary seismic station
• Strong motion• Broad band 360 second period to 200 Hz, with single jaw hole lock. • Two axis tilt meter with three jaw hole-lock • Hydrophone• High resolution Temperature sensor• Strain gauge, cemented
Thank You !
Matsushiro, Japan.
Installed April 2008Deployed at a depth of 700mCMG-3TB very broadband (VBB) velocity
sensor with response from 360s to 100Hz;
CMG-5TB strong motion sensor with response from DC to 200Hz;
CMG-DM24mk3 7-channel 24-bit downhole digitiser with serial to optical converter;
Single jaw hole lock (pressure compensated).
CMG-3TB Case Studies
Above a Magnitude 6.4 in Crete recorded on all four sensors
CMG-3TB Case Studies (Belgium)
Nuclear Explosion Treaty Monitoring
CMG-3TB Case Studies
The above sensors feature a bishop hat orientation module allowing them to use the original KS-54000 and KS-36000 holelock mechanisms retaining the same physical orientation in the Boreholes
CMG-3TB Case Studies