Automatic determination of depth phases and earthquake focal depth using Cepstral Stacking Method (CSM) and Standing Order of Data (SOD) Recep Cakir Lingsen Meng Michel Foundotos Chin-Wu Chen EarthScope USArray Data Processing and Analysis Short Course Student Project August 29, 2010 Northwestern University, Evanston-Chicago

Objectives Create an automatic process to detect depth phases (pP and /or sP) and determine focal depth Report focal depth additional to ones from USGS/IRIS/CMT/regional networks Report depth phases additional to ISC and regional network bulletins

Focal depth calculation Depths from pP and sP delay times h = source depth η = slowness pP sP P Focal Depth Surface of the Earth Earthquake Depth= h h Alexander and Cakir, 2010

an d Then or Cepstral Method S(t)=Observed eartquake signal a and b= amplitude and polarity of delayed signals Alexander and Cakir, 2010

P P wave pP + pP wave = pP-P delay time Seismic signal P pP Time (second) C1(u) Subwindow C1(t) C2(t) C3(t) C4(t) C1(u)+ C2(u)+ C3(u) Alexander and Cakir, 2010

Stacking by summing the subwindows Stacking by multiplying the subwindows Cepstral Stacking Method (CSM) Alexander and Cakir, 2010

Select Total Window Length (S – P Maximum) Select Start Time (P onset) Select Subwindow Length Select Percentage Overlap Calculate Cepstrum of ith Subwindow Product and/or Sum Stack Subwindow Cepstra (i= 1, N) Pick (non-zero) Delay Time(s) of Largest Cepstral Stack Peak(s) Select Known or Assumed Crustal Velocity Model for Station Calculate Source Depth from Delay Time of First Large Peak (pP – P) Calculate Source Depth from Second Large Peak (sP – P) Assign Final Source Depth from One or Both Depth Estimates CSM data processing workflow (in SAC) Alexander and Cakir, 2010

AUTOMATIC PROCESSING INITIALIZE PARAMETERS  Sub-Window Length (sec)  Percentage Overlap (%)  Stacking (product, sum, both)  Multiple Station Stacking (Y/N)  Display (all/final sub-stack plots)  Automatic Depth Estimation (Y/N) PROCESS Station k (k=1,M) STACK STATION CEPSTRA FINAL DEPTH ESTIMATE Master script (Matlab) SOD Download earthquake catalog and waveform data

SOD recipe

Matlab master script

Conclusion Rapid, automatic detection of depth phases and focal depth Integrate programming of SOD, Matlab, and SAC Discussion Estimation of focal mechanism Comparison with theoretical travel time prediction Quality control system Array processing enhances precision

References Alexander, S.S. and Cakir, R. (2010) Further Development of the Cepstral Stacking Method (CSM) for Accurate Determinations of Focal Depths for Earthquakes and Explosions., Seismo. Res. Let., 81, 2, p356, SOD manuals - Matlab manuals - SAC manuals -