A workflow for seismological new babies

[core-man]

1. Seismology Basis

   Please refer to https://migg-ntu.github.io/SeisTomo_Tutorials/seismology/index.html for seismological basis:

   • Introduction to Seismology
   • Seismic Source
   • Seismic Wave
   • Seismic Station
   • Seismic Data

2. Earthquakes near the Island of Hawaii

   The earthquake catalog can be found at the following two websites.

   • https://earthquake.usgs.gov/data/comcat/
   • http://www.isc.ac.uk/iscbulletin

3. Seismic stations near the Island of Hawaii

   Since you will work on seismic data in Hawaii, please have a quick look at seismic stations near the main island: http://ds.iris.edu/gmap/#network=*&maxlat=20.458&maxlon=-154.4943&minlat=18.8231&minlon=-156.5982&drawingmode=box&planet=earth

4. Data Fetching

   Please refer to some Python codes using the ObsPy package to download seismic data:

   • https://github.com/MIGG-NTU/SeisData_Tools/tree/main/workshops/SeisTomo_Tutoriala_DATA/data-fetch

5. Data Processing

   After we fetch seismic waveform data, we may want to pre-process them before we finally analyze them using cross-correlation or Machine Learning. Please refer to https://github.com/MIGG-NTU/SeisData_Tools/tree/main/workshops/SeisTomo_Tutoriala_DATA/data-process to learn some basic pre-processing, e.g.,

   • filter the data
   • mark first seismic wave arrival time

   SAC (http://ds.iris.edu/ds/nodes/dmc/forms/sac/) is a popular GUI software in the seismological community, which can be used to process and visually check seismic data.

6. Plotting data

   We usually have to plot figures in seismological studies, e.g., earthquake waveform wiggles, earthquake wiggles. PyGMT (https://www.pygmt.org/latest/) is a Python Interface for GMT, which is a commonly-used plotting software.
   Of course, you could use other software to plot figures.

7. A Preliminary workflow

   We should build a workflow before we work on all the earthquakes in Hawaii. So here are some suggestions if needed:

   • Download earthquakes near the main island of Hawaii and plot them on a map.
   • Only download seismic waveform data for earthquakes in one year, e.g., 2017 or 2018. This will save you time to download and process large datasets before you are familiar with seismic data.
   • The studying region is small, so 30 seconds before and 90 seconds after the earthquake occurring time (i.e., origin time) should be long enough.
   • Processing seismic data: filtering (e.g., bandpass 1-2 Hz) and mark first seismic wave arrival
   • Calculate cross-correlation for seismic data at the same station for two nearby earthquakes (e.g., an inter-event distance smaller than 10 km)