32 lines
1.2 KiB
Python
32 lines
1.2 KiB
Python
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from obspy import Stream
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from scipy.fft import rfft, rfftfreq
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from scipy.interpolate import interp1d
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import numpy as np
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def calculate_amp_spectra(station_stream: Stream):
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"""
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Function returns frequencies and corresponding mean amplitude spectra (for all available traces in stream).
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All spectra are interpolated
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:param station_stream:
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:return:
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"""
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# Fourier's transformation of signal for each trace (channel) in the stream
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freq_bins = None
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psd = 0
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for tr in station_stream:
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fft_signal = rfft(tr.data)
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freq_bins = rfftfreq(len(tr.data), d=tr.stats.delta)
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amp_spectrum = abs(tr.stats.delta * fft_signal) # Multiplication by sampling step
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amp_spectrum = amp_spectrum * np.sqrt(2) # Multiplication by square root to calibrate energy
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psd += amp_spectrum ** 2 # for calculation of root-mean-square
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# Calculation of root-mean-square for all traces in the stream
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mean_amp_spectra = psd ** 0.5
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# Interpolation
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fi = np.logspace(np.log10(freq_bins[1]), np.log10(freq_bins[-1]), len(freq_bins))
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interpolation_function = interp1d(freq_bins, mean_amp_spectra, kind='linear', fill_value='extrapolate')
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return fi, interpolation_function(fi)
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