10 Aug 2015 a significant quake M 6.6, Solomon Isl

[davenn]

Mw 6.6 180km SW of Dadali, Solomon Islands 2015-08-10 04:12:14 UTC

from my seismograph located in Sydney, Australia ...

the event below it was a M 5.2 NE of Raoul Is, Kermadecs, NZ
Dave

 

[DaveC426913]

Cool.

Does the deflection of the needle translate into some value with a unit? i.e. does an 10 millimeter spike correspond with a 10 centimeter ground movement, or some such correlation?

 

[davenn]

Hi Dave,

the seismometer used in the above recording is a Force Balanced Vertical seismometer
These record ground velocity rather than displacement

on this page you will see pic's of a completed one as well as one during assembly
Dale, the page owner build and calibrated my unit The instrument's final cost to me was AU$550

the spec's for the instruments he builds are ...

FBV INYO specifications

• 
  The instrument's high-gain output has a sensitivity of approximately 315 V/cm/sec (31,462 V/m/sec) over a frequency range of 50 seconds to 30 Hz, while the low gain output is 6.29 V/cm/sec (629 V/m/sec) over the same bandwidth. Both outputs clip at a level of 10 Volts, which represents 318μm/sec for the high gain channel and 1.59cm/sec for the low gain one.
  
  High gain channel
  
  354nm/sec/line *WinSDR Y-scale factor = 1 50sec – 12.5sec (0.08Hz) Clipping level 318μm/sec.
  
  These settings greatly reduce microseisms and cultural noise although they also eliminate higher-frequency local quakes and may mask some phases of teleseisms. However the sensitivity is sufficient to occasionally display surface waves originating from distant quakes having magnitudes in the high 4's, low 5's. Large quakes will be off screen, although the channel clipping level (10V out) is still 318μm/sec. or 36x this screen height.
  
  Low gain channel
  
  17.7μm/sec/line WinSDR Y-scale factor = 1 50sec – 10Hz Clipping level 1.59 cm/sec
  
  These settings clearly show some cultural noise, which tends to get smaller at night. Higher-frequency local quakes show up well on this display and large teleseisms are also well displayed.
  

* WinSDR is the datalogging software/hardware

Dave

 

[davenn]

another significant quake from the Solomons region this morning
Mw 6.4

 

[davenn]

yet another significant quake in the Solomons reg
M 6.6 SW of Santa Cruz Isl