Tsunami Detection?
April 2016
© 2016 Xtera Communications, Inc. Proprietary & Confidential
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What can be done and what can’t
(easily)
Stuart Barnes, Joerg Schwartz, Steve Desbruslais and Maria Ionescu
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Earthquakes, Impact
and Detection
• What are the tell-tale signals on the
seabed
•
•
•
•
Temperature drops
Pressure changes
Underwater waves
Shock waves
• Large external temperature changes
can be detected internally, but not
the changes likely to be seen remote
from the epicentre
• Underwater waves are only detected
if they move/shake the repeater
• Pressure changes can only be
detected outside the repeater due to
the hermetic characteristics
• Only an outside shock effect can
be truly detected “inside” a
repeater
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Benefit and impact of
having internal devices
• Temperature and shock
detection both feasible
• However there needs to be
some form of continuous
active supervisory to trigger
alerts at NMS in real-time
• There is some impact on cost
but minimal impact on
installation and usage (and
may in fact give a commercial
opportunity to cable owners)
• BUT do we know what we
are really trying to detect?
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Accelerometer measurements
from deep sea trial
Acceleration vs Time
1.50
DEPLOYMENT
RECOVERY
1.00
Repeater
on sea bed
Accerlation (g)
0.50
Repeater
on drum
engine
0.00
-0.50
Repeater
on deck
Repeater
movement
on sea bed
-1.00
Repeater lift-off
from sea bed
X Acceleration g
Y Acceleration g
Z Acceleration g
-1.50
1:00
3:00
5:00
7:00
9:00
11:00
13:00
15:00
17:00
19:00
Time
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The impact of external devices
• Any external sensors would have
to be located on the Bulkhead or
on a cable streamed away from
the repeater
• More sensitive devices can be
housed externally. But,
•
•
There is little “real estate” on a small
repeater
A third cable solution may look like that of
a Branching Unit (See opposite)
• This approach will have major
cost and risk impacts over and
above a standard deployment
• Are there smarter ways for
detection with less impact?
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What are the signatures
of an earthquake?
• Temperature
• Pressure
• Shock waves
•
•
•
•
Primary (P) waves (longitudinal)
Secondary (S) waves (transverse)
Surface waves (LR) (damaging)
3D accelerometers are sensitive to all
types of shock waves.
Seismogram from IRIS (Incorporated Research Institutions for Seismology)
• P-waves (compressional)
•
arrive first and can provide critical
tsunami warning-time.
http://www.geo.mtu.edu/UPSeis/waves.html
© 2016 Xtera Communications, Inc. Proprietary & Confidential
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Shock Detectors
• Earthquake shock waves travel
at least 10x faster than
tsunami waves.
• Shock waves detection can
thus provide an early warning
mechanism.
• The transmitted frequencies of
interest are 0.01-0.1 Hz, for
shock waves of earthquakes
of magnitude > 6.
• Accelerometers are ideal
sensors for:
•
•
Large local earthquakes
High-frequency seismic waves
• A variety of accelerometers
can be sourced with different
frequency responses, within a
frequency band of 0-100Hz.
• What is needed?
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Concluding Remarks
•
Accelerometers can be placed inside repeaters as a possible means of
providing Tsunami warnings
•
These can be installed with little installation and operational risk
and may provide a source of additional revenue to an operator
•
External sensors are much more problematical both from an
installation and maintenance perspective
•
Active supervisory solutions are needed to feedback information
– Our supervisory system sends data in both directions so it will automatically
arrive at the closest land point first
•
The frequency response range is unknown
– But if this be shown to work then this is a very low cost/easy to implement
solution
© 2016 Xtera Communications, Inc. Proprietary & Confidential
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About Xtera Communications, Inc.
Xtera Communications, Inc. (NASDAQ: XCOM) is a leading provider of high-capacity, cost-effective optical
transport solutions, supporting the high growth in global demand for bandwidth. Xtera sells solutions to
telecommunications service providers, content service providers, enterprises and government entities
worldwide. Xtera’s proprietary Wise RamanTM optical amplification technology leads to capacity and reach
performance advantages over competitive products. Xtera’s solutions enable cost-effective capacity to
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fueled by the development of data centers and related cloud-based services.
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