﻿THE 
  SEISMIC 
  FOCUS. 
  1 
  79 
  

  

  been 
  of 
  value 
  in 
  the 
  case 
  of 
  Shillong 
  and 
  Gauhati. 
  Details 
  of 
  these 
  

   are 
  given 
  in 
  Appendix 
  F, 
  from 
  which 
  it 
  will 
  be 
  seen 
  that 
  the 
  alleged 
  

   simultaneity, 
  when 
  critically 
  investigated, 
  means 
  intervals 
  of 
  from 
  

   4s. 
  to 
  im. 
  of 
  time. 
  It 
  must 
  be 
  noticed, 
  moreover, 
  that 
  the 
  records 
  are 
  

   not 
  concordant 
  ; 
  for 
  instance, 
  the 
  shock 
  of 
  5-48 
  A.M. 
  (Madras 
  time) 
  

   on 
  25th 
  October 
  is 
  reported 
  by 
  the 
  Shillong 
  office 
  to 
  have 
  been 
  felt 
  

   at 
  the 
  same 
  time 
  at 
  Gauhati, 
  while 
  the 
  Gauhati 
  office 
  reports 
  that 
  

   it 
  received 
  the 
  signal 
  from 
  Shillong 
  one 
  minute 
  before 
  the 
  shock 
  

   reached 
  Gauhati. 
  

  

  From 
  this 
  it 
  is 
  evident 
  that 
  the 
  time 
  intervals 
  were 
  not 
  always 
  so 
  

   short 
  as 
  to 
  necessitate 
  a 
  great 
  depth 
  of 
  focus. 
  They 
  might 
  be 
  ac- 
  

   counted 
  for 
  by 
  the 
  focus 
  lying 
  between 
  the 
  two 
  stations 
  or 
  to 
  one 
  side 
  

   of 
  the 
  line 
  joining 
  them, 
  in 
  such 
  a 
  way 
  that 
  the 
  distance 
  to 
  be 
  tra- 
  

   velled 
  was 
  nearly 
  the 
  same 
  in 
  either 
  case. 
  In 
  those 
  cases 
  where 
  the 
  

   shock 
  is 
  reported 
  to 
  have 
  been 
  felt 
  simultaneously 
  at 
  three 
  stations, 
  

   it 
  is 
  possible 
  that 
  a 
  large 
  area 
  was 
  set 
  in 
  motion, 
  practically 
  simul- 
  

   taneously, 
  along 
  a 
  horizontal 
  thrust-plane. 
  

  

  Taking 
  everything 
  into 
  consideration, 
  there 
  is 
  nothing 
  to 
  neces- 
  

   sitate 
  the 
  assumption 
  of 
  a 
  great 
  focal 
  depth, 
  if 
  this 
  is 
  inconsistent 
  

   with 
  the 
  conclusion 
  arrived 
  at 
  by 
  other 
  lines 
  of 
  reasoning. 
  

  

  Summing 
  up, 
  then, 
  we 
  may 
  say 
  that 
  the 
  earthquake 
  of 
  12th 
  June 
  

   1897 
  was 
  caused 
  by 
  a 
  movement 
  along 
  a 
  thrust-plane 
  or 
  thrust-planes 
  

   and 
  along 
  secondary 
  thrust- 
  and 
  fault-planes, 
  which 
  had 
  a 
  maximum 
  

   length 
  of 
  about 
  200 
  miles 
  and 
  a 
  maximum 
  width 
  of 
  about 
  50 
  

   miles. 
  The 
  depth 
  of 
  the 
  principal 
  fissure 
  cannot 
  be 
  determined, 
  but 
  

   was 
  probably 
  not 
  so 
  much 
  as 
  5 
  miles 
  below 
  the 
  surface, 
  and 
  numerous 
  

   secondary 
  faults 
  and 
  fractures 
  rose 
  from 
  it 
  towards, 
  and 
  in 
  some 
  

   cases 
  as 
  far 
  as, 
  the 
  surface 
  of 
  the 
  ground. 
  1 
  

  

  1 
  This 
  chapter, 
  was 
  written 
  before 
  the 
  results 
  of 
  the 
  reobservation 
  of 
  the 
  triangulation 
  of 
  

   the 
  Khasi 
  hills 
  was 
  received. 
  I 
  still 
  consider 
  it 
  represents 
  the 
  most 
  probaole 
  explanation 
  of 
  

   the 
  earthquake, 
  but 
  the 
  revision 
  of 
  the 
  triangulation 
  has 
  shown 
  that 
  it 
  may 
  possibly 
  be 
  

   incorrect. 
  These 
  results 
  were 
  received 
  too 
  late 
  to 
  be 
  incorporated 
  in 
  this 
  chapter, 
  they 
  are 
  

   discussed 
  in 
  Appendix 
  G, 
  at 
  the 
  end 
  of 
  which 
  will 
  be 
  found 
  a 
  statement 
  of 
  the 
  extent 
  to 
  which 
  

   the 
  conclusions 
  drawn 
  in 
  this 
  chapter 
  are 
  rendered 
  uncertain, 
  though 
  not 
  disproved. 
  

  

  N2 
  ( 
  179 
  ) 
  

  

  