﻿506 
  

  

  Geological 
  Society 
  

  

  downward 
  pressure 
  and 
  a 
  horizontal 
  stress 
  between 
  south 
  and 
  west 
  

   during 
  the 
  next 
  six 
  hours. 
  The 
  record 
  was 
  accordingly 
  grouped 
  by 
  

   the 
  successive 
  two-hour 
  periods 
  from 
  XII 
  to 
  XII 
  o'clock, 
  and 
  the 
  

   mean 
  amount 
  of 
  variation 
  in 
  the 
  stresses 
  was 
  calculated 
  for 
  the 
  

   same 
  periods. 
  The 
  result 
  is 
  set 
  forth 
  in 
  the 
  appended 
  tabular 
  

   statement 
  : 
  — 
  

  

  Distribution 
  op 
  Stresses 
  and 
  Shocks 
  in 
  Two-Hour 
  Periods, 
  

   before 
  and 
  after 
  mldday 
  and 
  mldnight. 
  

  

  Hours 
  XTT 
  TT 
  TTTT 
  VT 
  VTTT 
  X 
  YTT 
  

  

  

  

  Stresses. 
  

  

  Mean 
  range 
  of 
  stress 
  in 
  each 
  

   two-hours, 
  in 
  Italy. 
  

  

  Total 
  stress 
  

  

  Horizontal 
  component 
  

  

  Vertical 
  component 
  . 
  . 
  

  

  -•10 
  

   + 
  •07 
  

   -•14 
  

  

  -•27 
  

  

  -•11 
  

   -•27 
  

  

  -•23 
  +-23 
  

   -•20 
  +-20 
  

   -•13 
  , 
  +-13 
  

  

  + 
  •27 
  

   + 
  •11 
  

   + 
  •27 
  

  

  + 
  •10 
  

   -•07 
  

  

  + 
  •14 
  

  

  

  

  Shocks. 
  

  

  Ratio 
  of 
  actual 
  to 
  mean 
  fre- 
  

   quency 
  of 
  each 
  two-hour 
  

   period. 
  

  

  Italy, 
  1891-1910 
  

  

  1-06 
  

  

  1-17 
  

  

  1-01 
  

  

  •90 
  

  

  •88 
  

  

  •99 
  

  

  

  

  

  

  Japan, 
  Aftershocks 
  of 
  Mino- 
  

  

  Owari, 
  Oct. 
  28th, 
  1891 
  ... 
  

  

  Japan, 
  1885-1890 
  

  

  1-01 
  

   1-00 
  

  

  ■95 
  

   1-11 
  

  

  ■96 
  -97 
  

   •89 
  -98 
  

  

  1-08 
  1-03 
  

   1-03 
  -99 
  

  

  

  

  

  

  

  

  From 
  these 
  figures 
  it 
  is 
  seen 
  that, 
  while 
  there 
  is 
  no 
  apparent 
  

   relation 
  between 
  the 
  frequency 
  and 
  the 
  total, 
  or 
  the 
  horizontal, 
  

   stress, 
  there 
  is 
  a 
  close 
  one 
  with 
  the 
  variation 
  of 
  the 
  vertical 
  stress 
  ; 
  

   the 
  greatest 
  number 
  of 
  earthquakes 
  being 
  in 
  the 
  period 
  in 
  which 
  

   there 
  is 
  the 
  greatest 
  increase 
  of 
  downward 
  pressure 
  ; 
  as 
  the 
  rate 
  of 
  

   increase 
  diminishes 
  the 
  number 
  of 
  shocks 
  is 
  less, 
  suffering 
  a 
  further 
  

   diminution 
  as 
  the 
  pressure 
  begins 
  to 
  decrease, 
  and 
  reaching 
  its 
  mini- 
  

   mum 
  in 
  the 
  period 
  where 
  the 
  decrease 
  in 
  pressure 
  is 
  greatest, 
  

   increasing 
  again 
  in 
  the 
  same 
  way 
  to 
  the 
  maximum. 
  

  

  An 
  attempt 
  to 
  apply 
  the 
  same 
  method 
  to 
  the 
  Japan 
  record 
  gave 
  

   a 
  result 
  which 
  was, 
  at 
  first 
  sight, 
  contradictory 
  and 
  also 
  inconsistent 
  

   in 
  itself, 
  for 
  it 
  gave 
  an 
  absolute 
  maximum 
  at 
  the 
  time 
  when 
  the 
  

   Italian 
  gave 
  a 
  minimum, 
  with 
  another 
  maximum, 
  almost 
  as 
  great, 
  

   in 
  coincidence 
  with 
  the 
  Italian 
  ; 
  but, 
  in 
  any 
  comparison, 
  it 
  is 
  neces- 
  

   sary 
  to 
  allow 
  for 
  the 
  contrast 
  in 
  the 
  character 
  of 
  the 
  two 
  records. 
  

   The 
  Italian 
  does 
  not 
  contain 
  more 
  than 
  two, 
  or 
  at 
  most 
  three, 
  great 
  

   earthquakes 
  of 
  the 
  type 
  that 
  gives 
  rise 
  to 
  long-distance 
  records 
  

   (bathyseisms), 
  and 
  the 
  aftershocks 
  account 
  for 
  no 
  more 
  than 
  a 
  

   quarter 
  of 
  the 
  whole 
  record; 
  the 
  Japanese 
  record, 
  on 
  the 
  other 
  

   hand, 
  is 
  dominated 
  by 
  bathyseisms 
  and 
  aftershocks. 
  Not 
  only 
  

   does 
  the 
  region 
  give 
  origin 
  to 
  an 
  unusually 
  large 
  number 
  of 
  tele- 
  

   seisms, 
  or 
  bathyseisms, 
  but 
  aftershocks 
  form 
  fully 
  three-quarters 
  of 
  

   the 
  record, 
  and 
  nearly 
  a 
  half 
  consists 
  of 
  aftershocks 
  of 
  the 
  Mino- 
  

   Owari 
  earthquake 
  of 
  October 
  28th, 
  1891. 
  Taking 
  these 
  separately. 
  

  

  