﻿THE 
  UNFELT 
  EARTHQUAKE. 
  

  

  23* 
  

  

  as 
  well 
  as 
  the 
  various 
  instrumental 
  amplifications, 
  the 
  results 
  are 
  

   such 
  as 
  to 
  lead 
  to 
  the 
  conclusion 
  that 
  the 
  problem 
  of 
  the 
  seismic 
  

   motion 
  requires 
  a 
  different 
  solution 
  in 
  each 
  case. 
  

  

  In 
  the 
  first 
  phase 
  the 
  measured 
  amplitude, 
  after 
  allowing 
  for 
  the 
  

   respective 
  instrumental 
  amplifications, 
  is 
  as 
  follows 
  : 
  — 
  

  

  

  Rapid 
  movement 
  

   of 
  iih. 
  io.m. 
  

  

  _ 
  — 
  =sn 
  

  

  Slow 
  movement 
  

  

  OF 
  IIH. 
  47M. 
  

  

  

  E— 
  W. 
  

  

  N— 
  S. 
  

  

  Res. 
  

  

  E— 
  W. 
  

  

  N— 
  S. 
  

  

  Res. 
  

  

  

  mm. 
  

  

  mm. 
  

  

  mm. 
  

  

  mm. 
  

  

  mm. 
  

  

  mm. 
  

  

  (2) 
  Vasca 
  sismica 
  .... 
  

  

  o*2o 
  

  

  C05 
  

  

  0'2I 
  

  

  0*038 
  

  

  0*027 
  

  

  0*047 
  

  

  (3) 
  Seismometograph 
  

  

  O'lO 
  

  

  o'oo 
  

  

  O'lO 
  

  

  0*040 
  

  

  o'ooo 
  

  

  0*040 
  

  

  (5) 
  Spirit 
  levels 
  .... 
  

  

  2*CO 
  

  

  ? 
  

  

  2*0 
  

  

  9*0 
  

  

  6*o 
  

  

  iro 
  

  

  (7) 
  Water 
  levels 
  .... 
  

  

  0*040 
  

  

  0014 
  

  

  0O42 
  

  

  O'OIO 
  

  

  o'ooo 
  

  

  O'OIO 
  

  

  (8) 
  Horizontal 
  pendula 
  

  

  OM9 
  

  

  012 
  

  

  0*23 
  

  

  5*50 
  

  

  2*85 
  

  

  6*20 
  

  

  These 
  linear 
  amplitudes 
  may 
  be 
  converted 
  into 
  angular 
  values, 
  

   on 
  the 
  basis 
  of 
  the 
  equivalent 
  lengths 
  of 
  a 
  single 
  pendulum 
  to 
  which 
  

   the 
  instruments 
  correspond, 
  which 
  is 
  given 
  in 
  the 
  first 
  column 
  of 
  the 
  

   table 
  printed 
  below. 
  

  

  (2) 
  . 
  . 
  . 
  

  

  (3) 
  . 
  . 
  . 
  

   (5) 
  . 
  . 
  . 
  

  

  (7) 
  . 
  . 
  . 
  

   f 
  E. 
  W. 
  . 
  

  

  (8) 
  JN.S. 
  . 
  

   \ 
  Resultant 
  

  

  Equivalent 
  

   length 
  of 
  

  

  Angular 
  values. 
  

  

  pendulum. 
  

  

  nh. 
  19m. 
  

  

  nh. 
  47m. 
  

  

  Metres. 
  

  

  // 
  

  

  » 
  

  

  o75 
  

  

  57*8 
  

  

  i3'o 
  

  

  Too 
  

  

  20*8 
  

  

  8'2 
  

  

  412*00 
  

  

  To 
  

  

  55 
  

  

  1*10 
  

  

  7*9 
  

  

  2*1 
  

  

  417 
  

  

  10 
  

  

  27-2 
  

  

  45'2 
  

  

  o*6 
  

  

  i3'o 
  

  

  

  VI 
  

  

  30*1 
  

  

  ( 
  2 
  3 
  « 
  ) 
  

  

  