Name: Seisometer
Execution: Must have iOS 4.0 or higher

Instructions:
Lay the iPhone on a relatively flat surface with the screen facing up. Program will begin with Accelerometer readings via x, y, z-axis (positive z points up from screen). Initial readings should give x and y values of around 0, with z around -1. Once the iPhone is on the table, press the "Start" button (this will track the current z value in case the surface is not perfectly flat). Carefully shake the surface, simulating ground vibrations. This will cause the program to calculate the highest peak ground acceleration value and use this to calculate the Richter/Mercalli scales. Press "Reset" to reset the highest peak ground acceleration value. 

NOTE: Please do NOT forcefully shake the surface and/or iPhone. Do NOT throw your iPhone. For safest conditions, lay the iPhone on a relatively flat soft surface (like a bed). 

NOTE: This only gives a ROUGH estimate of the scales. Remember that a Richter Scale requires several seismograph readings of different locations in order to accurately give a reading (see below). 


Background:

This program uses the iPhone's built in accelerometer to estimate the Richter and Mercalli Intensity Scale via correlated peak ground acceleration data. The Richter scale is a logarithmic measure of Earthquake energy, determined from the maximum recorded excursion amplitude of a Wood-Anderson Seismometer reading and location of Seisometer from epicenter. The Mercalli Intensity Scale is a scale for measuring the intensity of an earthquake, estimating the noticeability and damage of the seismic waves. Peak ground acceleration is a measure of earthquake acceleration on the ground (measured as a fraction of g = 9.81 m/s^2). 

The formulated equation uses data from the US Atomic Energy Commission's Nuclear Reactors and Earthquakes paper. Figure 1.7A on page 14 of the document gives an approximate relation of Earthquake magnitude with energy release and epicentral acceleration. Thus the equation used for the Richter Scale assumes the epicenter is located nearby the device.

http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=4620608