Elsayed Fergany, PhD.  

Na$onal  Research  Ins$tute  of  Astronomy  &  Geophysics,    

Cairo,  Egypt.  

Email:    Elsayed_fergany@hotmail.com  

 

 

Overview  � Every  day  there  are  many  earthquakes  around  the  globe,  whose   seismic   signals   are   the   same   size   as   those   of  potential  underground  nuclear  explosions.    

�  Several   methods   can   be   applied   to   differentiate  earthquakes   from   underground   nuclear   explosions.  However,  no  one  method  is  completely  reliable.    

� An  on-­‐site  inspection  is  a  meticulous  search  of  a  clearly  defined   inspection   area   to   gather   evidence   on  whether  or  not  a  nuclear  explosion  has  taken  place.    

Overview  Cont.  � Rapid   deployment   into   the   Field,   CTBTO   has   only   six  days  from  receiving  the  inspection  request  to  transport:    �  1)Inspection  team  of  40  inspectors  (including  experts  in   seismology,   geophysics,   radionuclides,   radiation  protection,  communications,  logistics,  and  IT),  

�  2)  ~100  tons  of  equipment  into  the  country  subjected  to  the  inspection.    

� The   inspection   is   scheduled   to   last   60   days   and   can   be  extended  to  a  maximum  duration  of  130  days.  

Mo;va;on  � Huge   challenges   of   time   and   economic   costs   to   deploy  the  On-­‐Site  Inspection.  

� On   the   other   hand,   every   day   ~500,000   new   born  humans   allover   the   world.   Every   human   has   a   specific  genome   (DNA)   which   distinguishes   each   person   from  another.  

� The  motivated  principal  question  is  that:  Is   it   possible   to   identify     a   distinguishing   feature  (signature)   of   each     event   type   (natural   and  artificial)  like  that  in  humans?    

Aims  of  Work  � Search   for   a   distinguishing   feature   or  signature  of  each  event  type  of  natural  and  artificial  events.  

� Apply   or   develop   advanced   analysis   tools  for   identifying   the   signature   of   each   event  type.  

Data  Records    �  Four  seismic  waveforms  were  requested  and  downloaded  

from   the   Incorporated   Research   Institutions   for  Seismology,  IRIS.    

� Two  of   these  seismograms  are  North  Korea  nuclear   tests  in   2009   and   2013,   and   the   other   two   seismograms   are  earthquakes.  

� The  four  seismograms  were  selected  and  grouped  as  two  sets.  

� Each   set   included   two   events   (an   earthquake   and   a  nuclear  explosion)  of  the  same  magnitude  recorded  at  ~  the  same  distance.    

�    North   Korea   nuclear   explosion   (MB   =   4.7)   on   25   May  2009  recorded  at  MDJ  3.35o,  

�  Solomon   Islands   earthquake   (MB   =4.7)   on   23   May   2015  recorded  at  HNR  station  at  distance  3.29o.  

 

Set  1  

� North  Korea  nuclear  explosion  (MB=5.1)  on  12  February  2013  recorded  at  MDJ  3.35o,  

�  Sichuan,   China   earthquake   (MB   =   5.1)   on   01   October  2014  recorded  at  KMI  station  at  distance  3.28o.  

Set  2  

Data  Analysis  � The  analysis  of  seismic  waveform  is  based  on  the   idea  of  using  the  H/V  spectral  ratio  of  ambient  noise  to  estimate  the  site  characteristics.  

�  In  this  study,  the  spectral  ratio  of  seismic  event  and  pre-­‐event   noise   of   the   same   component   is   calculated   to  identify  the  predominant  period  (signature)  of  each  event  type.  

� By  this  way,  the  receiver  and  Site  effects  are  canceled,  and    reveals  the  source  and  path  effects  of  the  seismogram.  

� The  feature  of  the  predominant  period    for  each  event  type   is   identified  using  spectral  ratio  of   long  window  of  event  and  pre-­‐event.  

� The  predominant  period  is  that  has  highest  amplitude  for  longest  time.  

�   Geopsy  code  is  used  to  calculate  the  spectral  ratio  for  each   component   of   all   four   events   along   window  length  of  900  s  (15  minutes).  

North  Korea  nuclear  explosion  (MB=5.1)  

Sichuan,  China  earthquake  (MB  =  5.1)    

Results          Set  1,  Z-­‐Comp.  

NK2009_MDJ-­‐Z_900s   2015-­‐05-­‐23  MB4.7  Solomon  Islands  

     

Set  1,  E-­‐Comp.  E  

 

E  

   

Set  1,  N-­‐Comp.    N

 

 N  

   

Set  2,  Z-­‐Comp.  NK2013_Z_900s   SI_China2014_Z_900s  

     

Set  2  ,  E-­‐Comp.  E  

 

E  

   

Set  2  ,  N-­‐Comp.  N  

 

N  

   

Discussion    � The   spectral   ratio   of   Event/Pre-­‐Event   for   each  component   of   the   two   sets   using   a   simple   analysis  tool  of  Geopsy.  

� Using  a  window    of  15  m  is  based  on  trials,  where  after  15  m  of  event  time  the  event  signals  are  disappeared.    

         � The  predominant  period  of  each  event  is  inferred.  

Discussion  cont.  � The  dominant  period  of  nuclear  explosions  is   inferred  at  higher  frequency  ~  1  Hz  for  each  component  of  the  two  explosions.    

� The   dominant   period   of   earthquakes   is   inferred   at  three  lower  frequencies  0.5,  0.1  and  0.o5  Hz.  

� The  highest  one   in  amplitude  varies   from  component  to  other  for  the  same  earthquake.    

� These  multiple  dominant  periods   in   earthquakes  may  be  due  to  the  fault  rupture  process.  

Conclusions  &  Recommenda;ons  � The   idea   of   the   work   is   based   on   the   motivated  question  of  imitating  genome-­‐specific  human  nature.  

� Based   on   using   of   event/pre-­‐event   spectral   ratio,   we  deduce  that:  

Ø Nuclear  explosions  are  characterized  by  one  shorter  predominant  period  (~  1  Hz).  

Ø Earthquakes   are   characterized   by   multiple   longer  dominant   periods   (0.5,   0.1,   0.05   Hz),   and   the  predominant  one  varies  from  component  to  another.  

�  The   difference   in   the   predominant   period   and   spectral  ratio  shape  between  explosions  and  earthquakes  interprets  the  difference  of  source  mechanisms  for  each  one.        

� This   work   is   one   step   of   long   way   to   answer   the  principal  motivated  question.  

 � Although  it  looks  difficult  to  identify  the  signature  of  each  event  type,  it  is  not  impossible.  

 � This  signature  will  verify  the  type  of  each  event  at  the  data  center  within  few  minutes  of  the  event  time.  

� By  this  way,  the  CTBTO  can  save  time  and  cost  of  On  Site  inspection.  

� The   author   recommend   strongly   the   CTBTO   to  plan   for   a   significant   project   for   developing  advanced   measurements   and   analysis   tools   that  can   be   used   to   prove   this   reasonable   verification  idea.