1. ObsPy是什么？ ObsPy is an open-source project dedicated to provide a Python framework for processing seismological data. It provides parsers for common file formats, clients to access data centers and seismological signal processing routines which allow the manipulation of seismological time series. The goal of the ObsPy project is to facilitate rapid application development for seismology. 2. ObsPy

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The duration of strong earthquake ground motion is one of the main parameters characterizing this natural phenomenon. In Kanarnori and Anderson (1975)1, faulting duration is defined as $ t = L / v $ where $t$, $L$ and $v$ are duration of faulting, fault dimension and average propagation velocity, respectively. It’s hardly possible to obtain faulting duration by measuring fault dimension and propagation velocity. However, source duration can be attained from source time function or the envelope of waveforms [e.

Magnitude was the first quantitative measure of earthquake size based on seismograms. The maximum or “peak” ground motion is defined as the largest absolute value of ground motion recorded on a seismogram. Taking the 2011-03-11 Tohoku great earthquake as an example, at first, download broad-band seismic data in vertical direction from the global seismic stations (GSN) using Web Service Fetch scripts, and then convert data format from miniseed to SAC with software mseed2sac.

Last step, calculate energy distribution and plot result. By now, we have finished back-projection for waveforms. Next we need to summarize results back-projected from waveforms. $ csh sum_energy.csh # open sum_energy.csh to look over all commands Duplicate Read every grid’s stacked amplitudes. # open mkcontour_max_smo-multi-V2.0.f to look over full commands call system('ls stack.out > stackoutfiles') open (10, file='stackoutfiles') nth_BP = 0 do read(10,'(a80)',iostat=iostat) ss; if (iostat.ne.0) exit nth_BP = nth_BP + 1 filename(nth_BP) = ss end do close(10) Smooth and normalize # Open mkcontour_max_smo-multi-V2.

The part is main body of Back-projection. After preprocessing in a low frequency band, waveforms have been aligned preliminarily. Next we start to cross correlate with a higher frequency band and stack waveforms for all grid points. set cl = 2 # upper bound of low frequency band set ch = 0.5 # lower bound of low frequency band $ csh back-projection_2.csh # open back-projection_2.csh to look over all commands

Now, all the preparations have been done. Let’s start the key part of back-projection. We often cross correlate waveforms in a relatively lower frequency band, and then crosse correlate for a higher frequency bands again. This two-step procedure gives a good high-frequency station correction and avoids errors that may be caused by cycle slip in the higher frequencies. Copy all seismic files that have been checked in the Chapter 2, make sure that there are not repeating stations and all files have an equal delta.