﻿2 
  DR. 
  CHAELES 
  DAVISON 
  ON 
  THE 
  [Feb. 
  1897, 
  

  

  II. 
  Methods 
  of 
  representing 
  the 
  Distribution 
  oe 
  the 
  Shocks. 
  

  

  2. 
  The 
  great 
  earthquake 
  occurred 
  on 
  October 
  28th 
  at 
  6 
  h 
  38 
  m 
  a.m. 
  

   (mean 
  time 
  <of 
  135° 
  E.), 
  and 
  during 
  the 
  first 
  few 
  days 
  the 
  after- 
  

   shocks 
  were 
  so 
  numerous 
  and 
  were 
  separated 
  by 
  intervals 
  of 
  time 
  

   so 
  short 
  that 
  the 
  identification 
  of 
  many 
  of 
  those 
  observed 
  at 
  different 
  

   places 
  was 
  nearly, 
  if 
  not 
  quite, 
  impossible. 
  But 
  at 
  the 
  meteoro- 
  

   logical 
  station 
  of 
  Gifu, 
  and 
  at 
  thirty-two 
  other 
  places 
  in 
  the 
  provinces 
  

   of 
  Mino, 
  Owari, 
  and 
  Mikawa, 
  careful 
  records 
  were 
  kept 
  of 
  all 
  the 
  

   shocks 
  observed. 
  Plotting 
  on 
  a 
  map 
  the 
  numbers 
  corresponding 
  to 
  

   the 
  different 
  stations, 
  Prof. 
  Omori 
  has 
  drawn 
  curves 
  through 
  all 
  

   places 
  where 
  equal 
  numbers 
  of 
  shocks 
  were 
  felt 
  during 
  given 
  intervals 
  

   of 
  time 
  — 
  namely, 
  1892, 
  1893 
  (omitting 
  the 
  months 
  of 
  January 
  and 
  

   September), 
  January 
  1894, 
  and 
  also 
  during 
  the 
  four 
  years 
  1887 
  to 
  

   1890. 
  In 
  the 
  first 
  of 
  these 
  maps, 
  1 
  the 
  marked 
  expansion 
  of 
  the 
  

   curves 
  in 
  four 
  directions 
  indicates 
  the 
  existence 
  of 
  as 
  many 
  axial 
  

   lines 
  which 
  radiate 
  from 
  a 
  point 
  near 
  Koori, 
  and 
  along 
  which 
  

   the 
  seismic 
  activity 
  exceeded 
  that 
  in 
  the 
  adjoining 
  districts. 
  In 
  

   the 
  second 
  and 
  third 
  maps, 
  the 
  axial 
  lines 
  proceeding 
  towards 
  Ibi 
  

   and 
  the 
  Ise 
  Gulf 
  become 
  insignificant, 
  the 
  other 
  two, 
  extending 
  

   towards 
  the 
  E.N.E. 
  and 
  E.S.E., 
  being 
  still 
  distinct 
  ; 
  while 
  in 
  the 
  

   fourth 
  map 
  no 
  trace 
  of 
  any 
  one 
  of 
  the 
  axial 
  lines 
  exists. 
  One 
  

   interesting 
  result 
  which 
  these 
  maps 
  bring 
  out 
  very 
  clearly 
  is 
  that 
  

   in 
  the 
  central 
  part 
  of 
  the 
  Neo 
  Valley, 
  which 
  formed 
  the 
  principal 
  

   epifocal 
  tract 
  of 
  the 
  great 
  earthquake, 
  the 
  after-shocks 
  were 
  much 
  

   less 
  numerous 
  than 
  in 
  the 
  regions 
  to 
  the 
  north 
  and 
  south. 
  

  

  3. 
  The 
  maps 
  (figs. 
  2-8, 
  pp. 
  4-7) 
  which 
  illustrate 
  this 
  paper 
  are 
  

   founded 
  entirely 
  on 
  Prof. 
  Milne's 
  catalogues. 
  These 
  give, 
  with 
  com- 
  

   paratively 
  few 
  exceptions, 
  the 
  following 
  elements 
  of 
  each 
  earth- 
  

   quake: 
  — 
  the 
  time 
  of 
  occurrence, 
  the 
  length, 
  breadth, 
  and 
  extent 
  of 
  

   the 
  disturbed 
  area, 
  the 
  course 
  of 
  its 
  boundary, 
  and 
  the 
  approximate 
  

   position 
  of 
  its 
  epicentre. 
  Eor 
  the 
  latter 
  purpose, 
  the 
  whole 
  country 
  

   is 
  divided 
  by 
  north-south 
  and 
  east-west 
  lines 
  into 
  rectangles, 
  each 
  J 
  

   degree 
  in 
  length 
  and 
  breadth 
  ; 
  and 
  the 
  position 
  of 
  an 
  epicentre 
  is 
  

   represented 
  by 
  the 
  number 
  of 
  the 
  rectangle 
  in 
  which 
  it 
  occurs, 
  or, 
  if 
  

   under 
  the 
  sea, 
  by 
  its 
  distance 
  from 
  the 
  nearest 
  rectangle 
  on 
  land. 
  

  

  The 
  area 
  included 
  within 
  the 
  maps 
  is 
  bounded 
  by 
  the 
  parallels 
  

   34° 
  40' 
  and 
  36° 
  20' 
  lat. 
  N„ 
  and 
  by 
  the 
  meridians 
  2° 
  10' 
  and 
  3° 
  50' 
  

   long. 
  "W. 
  of 
  Tokio, 
  so 
  that 
  ten 
  of 
  Prof. 
  Milne's 
  rectangles 
  adjoin 
  each 
  

   side 
  of 
  the 
  map, 
  and 
  the 
  whole 
  area 
  contains 
  one 
  hundred 
  such 
  

   rectangles. 
  

  

  In 
  constructing 
  the 
  maps, 
  the 
  number 
  of 
  epicentres 
  lying 
  within 
  

   each 
  rectangle 
  has 
  been 
  counted. 
  Sometimes 
  an 
  epicentre 
  is 
  

   defined 
  as 
  lying 
  between 
  two 
  consecutive 
  rectangles, 
  and 
  such 
  

   cases 
  are 
  divided 
  equally 
  between 
  them. 
  2 
  Curves 
  are 
  then 
  drawn 
  

   through 
  the 
  centres 
  of 
  all 
  rectangles 
  within 
  which 
  the 
  number 
  of 
  

   epicentres 
  is 
  the 
  same, 
  or 
  through 
  points 
  which 
  divide 
  the 
  line 
  

  

  1 
  A 
  reduced 
  copy 
  of 
  this 
  map, 
  showing 
  its 
  essential 
  features, 
  is 
  given 
  in 
  

   'Natural 
  Science,' 
  vol. 
  vi. 
  (1895) 
  p. 
  393. 
  

  

  2 
  It 
  thus 
  happens 
  sometimes 
  that 
  the 
  number 
  of 
  epicentres 
  allotted 
  to 
  a 
  

   rectangle 
  is 
  not 
  integral. 
  

  

  