﻿172 
  DR. 
  C. 
  DAVISON 
  ON 
  THE 
  PEMBROKE 
  EARTHQUAKES 
  [May 
  I 
  897,- 
  

  

  (ii) 
  After- 
  Shocks, 
  

   b. 
  November 
  2nd 
  : 
  6.1 
  p.m. 
  

  

  Intensity, 
  4. 
  — 
  Number 
  of 
  records, 
  64; 
  from 
  57 
  different 
  places. 
  

  

  This 
  shock 
  was 
  felt 
  over 
  the 
  greater 
  part 
  of 
  Pembrokeshire 
  and 
  

   Caermarthenshire 
  and 
  in 
  the 
  southern 
  part 
  of 
  Caerdigansbire. 
  The 
  

   disturbed 
  area 
  is 
  43 
  miles 
  long, 
  29 
  miles 
  broad, 
  and 
  contains 
  about 
  

   1000 
  square 
  miles. 
  The 
  longer 
  axis 
  is 
  directed 
  about 
  E. 
  25° 
  NV 
  

   and 
  "W. 
  25° 
  S., 
  and 
  the 
  centre 
  of 
  the 
  area 
  lies 
  2\ 
  miles 
  north-west 
  

   of 
  Narberth, 
  that 
  is, 
  about 
  8 
  miles 
  "W. 
  20° 
  S. 
  of 
  the 
  centre 
  of 
  the 
  

   isoseismal 
  6 
  of 
  the 
  principal 
  earthquake. 
  The 
  line 
  joining 
  the 
  

   two 
  centres 
  is 
  thus 
  roughly 
  parallel 
  to 
  the 
  longer 
  axes 
  of 
  both 
  

   curves. 
  (See 
  map, 
  p. 
  158.) 
  

  

  The 
  shock 
  was 
  felt 
  at 
  45 
  places, 
  at 
  15 
  of 
  which 
  the 
  sound 
  was 
  

   not 
  heard. 
  The 
  sound 
  was 
  heard 
  at 
  22 
  places, 
  and 
  at 
  10 
  of 
  these 
  

   the 
  shock 
  was 
  not 
  felt. 
  So 
  far 
  as 
  the 
  observations 
  extend, 
  however,; 
  

   the 
  disturbed 
  area 
  and 
  the 
  sound-area 
  approximately 
  coincide. 
  

  

  The 
  shock 
  is 
  always 
  described 
  as 
  a 
  tremulous 
  motion, 
  as 
  a 
  rule 
  

   exceedingly 
  slight. 
  The 
  rumbling 
  sound 
  was 
  also 
  very 
  faint, 
  and 
  

   it 
  is 
  not 
  surprising 
  that 
  it 
  should 
  have 
  escaped 
  notice 
  at 
  many 
  

   places. 
  

  

  c. 
  November 
  2nd 
  : 
  about 
  6.15 
  or 
  6.30 
  p.m. 
  

  

  This 
  was 
  an 
  exceedingly 
  slight 
  shock. 
  It 
  was 
  felt 
  at 
  Llandyssul 
  

   and 
  Blaendyffryn 
  in 
  Caerdigan 
  shire, 
  possibly 
  also 
  at 
  Llanstinan 
  and 
  

   Pen-ty-parc 
  in 
  Pembrokeshire, 
  though 
  the 
  last 
  two 
  places 
  are 
  at 
  

   some 
  distance 
  from 
  the 
  others. 
  The 
  epicentre 
  obviously 
  lies 
  north- 
  

   east 
  of 
  that 
  of 
  the 
  principal 
  earthquake. 
  

  

  d. 
  November 
  3rd 
  : 
  about 
  1 
  a.m. 
  

  

  The 
  only 
  records 
  of 
  this 
  slight 
  shock 
  come 
  from 
  Llanilar 
  and! 
  

   Khydlewis 
  in 
  Caerdiganshire, 
  and 
  Newcastle 
  Emlyn 
  on 
  the 
  border 
  of 
  

   that 
  county 
  and 
  Caermarthenshire. 
  They 
  appear 
  to 
  indicate 
  a 
  still 
  

   further 
  displacement 
  of 
  the 
  epicentre 
  towards 
  the 
  north-east. 
  With 
  

   regard 
  both 
  to 
  this 
  and 
  the 
  preceding 
  shock, 
  it 
  should 
  be 
  remarked 
  

   that, 
  except 
  their 
  proximity 
  in 
  time 
  of 
  occurrence 
  and 
  disturbed 
  

   area, 
  there 
  is 
  no 
  evidence 
  for 
  connecting 
  them 
  with 
  the 
  same 
  fault- 
  

   system 
  as 
  the 
  first 
  two 
  earthquakes. 
  

  

  III. 
  — 
  Origin 
  op 
  the 
  Earthquakes. 
  

  

  In 
  correlating 
  the 
  earthquakes 
  described 
  above 
  with 
  the 
  faults 
  

   of 
  the 
  epicentral 
  district, 
  difficulties 
  arise 
  from 
  the 
  great 
  number 
  of 
  

   known 
  faults 
  in 
  one 
  part 
  and 
  their 
  scarcity 
  in 
  another. 
  The 
  

   majority 
  so 
  far 
  traced 
  are 
  longitudinal 
  faults, 
  and, 
  in 
  the 
  south 
  of 
  

   Pembrokeshire, 
  run 
  roughly 
  in 
  an 
  east-and-west 
  direction, 
  trending 
  

   some 
  degrees 
  north 
  of 
  east 
  in 
  the 
  west 
  of 
  Caermarthenshire. 
  It 
  can 
  

   hardly 
  be 
  doubted 
  that 
  a 
  series 
  of 
  transverse 
  faults 
  crosses 
  them 
  

   approximately 
  at 
  right 
  angles, 
  though 
  few 
  are 
  [marked 
  on 
  the- 
  

  

  