A Combined Denoising Method for Microseismic Signals from Coal Seam Hydraulic Fracturing: Multithreshold Wavelet Packet Transform and Improved Hilbert-Huang Transform

Figure 9

MWPT-IHHT method applied to real CSHF signals. (a) Signal #1 with high SNR. (b) Signal #2 with low SNR.

(a)

(b)