Hajime Shiobara

International Ocean Bottom Seismometer Special Interest Group Meeting
NSF-OBSIP, 15 Dec. 2015
NX-2G : autonomous BBOBS-NX for
a highly mobile broadband seismic
and tilt observation
at the seafloor
1, Hiroko Sugioka2*, Aki Ito2,
Hajime
Shiobara
Japanese OBS topics after the OBSIP WS in 2013.
and Masanao Shinohara1
1 ERI,
University of Tokyo
2 D-EARTH, JAMSTEC
* Fac. Sci., Kobe University
BBOBS-NX (NX-1G)
KAIKO7000II
Recorder unit
Housing : 65cm Ti
sphere
Max. depth : 6000 m
Sensor : CMG-3T
360s special (3comp.
Sensor unit
separated)
Max. tilt : ±8°, no
leveling mechanism
Clock : CSAC
Data media : SD-XC
Sensor unit
Recorder unit
BBOBS-NX (NX-1G)
Improved
horizontal noise
level as more than
20 dB.
STD
Comparable to
land station’s
noise level.
NX
More usable data
from temporal
observations.
Final BBOBS-NX (NX-2G)
 
 
 
BBOBS + NX-1G => NX-2G
  Goal of the BBOBS-NX development since 2002.
Autonomous system for high mobility with NX data
  No use of ROV : High mobility and more opportunity
  Separated burial sensor for high quality data
Self deployment & pop-up recovery
  Breakthrough of seismology in oceanic area
Known problems to be cleared for the NX-2G
  Tilt on landing over allowance range : about 50 %
  Extraction of sensor from sediments : ~ 80 kgw
  External design as the autonomous system
TiltHow
ontolanding
of NX-1G
clear this problem
?
### Reduce tilt below the allowance range ###
Two more
  Active posture control in descending like as the AUV
landings within
  When tilt occurred, descending or penetration
?
the range exist
with no tilt data.
### Accept tilt over the allowance range
###
Successful ones
  Widen the tilt allowance range of the sensor
were 53%.
  Re-design the CMG sensor requires time.
 
Equip leveling mechanism as
 
 
NM02P/03P: Pilot study
BBOBSNX2/3/4: Experiments
TNX-1/2: BBOBS”T”-NX
Sensor package becomes larger …
tilts were
Change to acceleration sensor for anyLarge
direction
corrected by using
  Power consumption, internal noise in long periods
a skid of the ROV.
Toward the
NX-2G
To understand the tilt
on landing, deep sea
video cam and MEMS
acceleration logger are
attached on the NX-1G.
First result was taken in
23 Sep. 2015, near
Japan Trench.
Toward the NX-2G
The
Maximum
tilt looksacceleration
determined on
at the
landing
moment
was of
about
the landing.
2.2 g.
New
style Ultra DeepofOBS
: NUDOBS
Development
NUDOBS
Buoyancy:
glass sphere
floats for 12
km depth
Transitions:
2 steps of
mechanical
function by
the acoustic
transponder
No rubber
molded
cable used.
FCU
SRU
This concept was based on the BBOBS-NX.
It is still a “proto-type” model.
Long-term test observation
of
Development
of NUDOBS
NUDOBS (and BBOBST-NX)
Deployed during
NT13-07,
April
20132014 was failed due to
Recovery
in April
at no
SE reply
off Boso
fromPen.
the NUDOBS.
NUDOBS
at P2reason
Possible
• 9200
m depthof glass floats made serious
• Implosion
damage
on the transducer.
• good
acoustic
condition
for status
• Malfunction
of electronic circuits in the
reply
of 1st transponder.
transition
acoustic
BBOBST-NX
at P1 reverse action of the pin
• Slow mechanical
to system
high pressure at 9200m depth.
• tiltdue
obs.
based on the NX
Plan of the NX-2G system
The mechanism to perform two transitions along three
stages is the key of this system. Qualitative design
consideration is still on the way.
Acceleration sensor for NX-2G ?
Paroscientific’s acceleration sensor by quartz resonators is
small and low power. Its true performance is evaluated now
with CMG-3Ts at the vault until Mar. 2016.