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