ifc: use scipy fftconvolve instead of numpy convolve.

src/ifc.py

 import sys
 import logging
 import numpy as num
+from scipy.signal import fftconvolve
 from pyrocko.guts import Object, String, Float
 from pyrocko import trace, autopick, util
 from lassie import shifter, common
@@ -60,13 +61,12 @@ class WavePacketIFC(IFC):
             tr.highpass(4, self.fmin, demean=True)
             tr.lowpass(4, self.fmax, demean=False)
             tr.ydata = tr.ydata**2
-
+            
             n = int(num.round(1./fsmooth / tr.deltat))
             taper = num.hanning(n)
-            tr.set_ydata(num.convolve(tr.get_ydata(), taper))
+            tr.set_ydata(fftconvolve(tr.get_ydata(), taper))
             tr.set_ydata(num.maximum(tr.ydata, 0.0))
             tr.shift(-(n/2.*tr.deltat))
-
             try:
                 tr.downsample_to(deltat_cf, snap=True, demean=False)
             except util.UnavailableDecimation as e: