Seismic Analysis 101

A seismologist need to master basic knowlegde of physics, math, and seismology. Besides that, you also need to master some basic skills in programming.

Operation System

There are three most commonly used operation systems for personal computers:

1. Microsoft Windows
2. Apple macOS
3. Linux (CentOS, Red Hat, Ubuntu, Debian, ...)

Most seismologists choose macOS or Linux as their primary operation system for daily researches, because both macOS and Linux provide easy access to toolchains needed in programming, and most existing programs/codes/packages for seismological researches were written on Linux and only work on Linux and macOS. As a beginner, you should use macOS or Linux.

For people who have a MacBook, MacBook Pro or iMac, you need to install the "Command Line Tools for Xcode" and Homebrew, then you're almost all set.

For people without access to macOS, you need a Linux OS. There're several ways to have a Linux OS (Linux itself is free):

1. Remove Windows completely and then install Linux (Danger! Make sure you understand what you are doing.)
2. Install Linux and Windows side by side (Danger! Make sure you understand what you are doing.)
3. For Windows 10 users, you can install Windows Subsystem for Linux (WSL) on your Windows 10, just like installing any other Windows softwares. It may behave very similar to the pure Linux OS, but I have never tried it.
4. MSU HPCC hosts some Linux servers, which are freely available to MSU researchers. You can use Windows on you own PC and use the Linux OS provided by HPCC remotely. It may be the most simplest and safest way to try Linux for beginners, although it's not very convenient.

Linux/macOS basis and Command Lines

Seismologists usually use command lines (CLI) rather than Graphic User Interface (GUI) to navigate around different folders/directories, run programs, process data and almost everything you can imagine, because using CLI is usually much efficient than using GUI. See Linux 101 for details.

Compiled Language

You need at least master one compiled language. The most popular compiled languages used in seismology community are C, Fortran, C++ and Java.

For beginners, C or Fortran are the best choices. You need to know the basic grammar of a programming language and how to compile/run a program.

For a program written in C or Fortran, you need follow the steps to run the program:

1. Write the source codes using the correct syntax
2. Compile the source codes to a executable file, using a compiler (`gcc` for C, `gfortran` for Fortran)
3. Run the executable file

To compile source codes to a executable file, you need to know some commonly used options for gcc and gfortran, such as -c, -o, -g, -I, -L, -l. It would be easier to solve some compilation errors if you have a basic understanding of the compiling, linking and executing for compiled languages.

You also need to learn how to read and write a Makefile, which is a tool to automatize the compiling process for a large source codes with multiple executable files

Interpreted Languages

Interpreted Languages can also be called as scripting language. It's usually easier to write and can accomplish complex tasks using only a few lines of codes. The only disadvantage is interpreted languages are usually much slower than compiled languages.

There are many interpreted languages, the most used in seismology community are bash, Python and Matlab.

Seismological Tools

This is a list of seismological tools you may use in your daily research. Please refer to this link for details.

• Seismic Analysis Code (SAC): SAC is the most commonly used data processing software for seismology.
• TauP: TauP is a software to calculate traveltimes of seismic waves trough the interior of the Earth.
• GMT: Plotting beautiful figures in publication-ready quality.
• SOD: Request seismic data from IRIS and other data center.