iTemblor Earthquake Simulator vs iSeismometer

Use iTemblor to explore the relationship between acceleration you impart on your phone and earthquake shaking intensity, based on the Modified Mercalli Intensity (MMI) scale. While the familiar Richter earthquake magnitude relationship (and others) scale with recorded ground movement, the MMI scale is a qualitative or observational scale of earthquake shaking intensity developed for comparing earthquake effects in locations where there are no seismographs. The Seismoscope View - The seismoscope is one of the oldest earthquake measurement devices, dating back to ancient China, and records the intensity and direction of shaking in the horizontal plane. In the spirit of the seismoscope, it’s most accurate to use this view by placing your phone on a flat surface (or hold it roughly horizontal) and to shake it horizontally. The movements you impart, plotted in 2D, are measured as acceleration in time which is then converted into MMI values using an empirical relationship between ground acceleration and MMI shaking intensity (Richter, 1958, Western United States). The Time Series View - The time series view is a traditional seismogram view that plots the accelerations you impart to your phone in 3 dimensions (x, y and z axes). You will see two traces for each axis, orange and green. The orange represents the raw acceleration data with the effects of gravity removed. The green represents the same data after the application of a low pass filter. The low pass filter is used to dampen your input to stay approximately within the frequency bandwidth of large earthquakes. The continuous time series is approximately 10 seconds long and is plotted in units of % gravity (G) The Data - iTemblor records the accelerations you impart onto your device and subtracts the effect of gravity. Then, a low pass filter is applied to constrain the recordings to stay within the bandwidth of large earthquakes (less than 10 hertz). The seismoscope view displays the fully filtered signal (equivalent to the green trace in the time series view). The time series view displays two traces. Both have gravity removed. The green trace has been low pass filtered (as described) and the orange trace has not. iTemblor is designed to provide fun and interesting correlations between the accelerations you impart on your iPhone through shaking and earthquake intensity. Efforts have been made to create generalized and realistic representations using published empirical data. Earthquakes are very complex and variable processes, therefore, iTemblor results should be viewed as approximate at best and be used for educational and entertainment purposes only.

iSeismometer turns your iPhone or iPad into a seismograph. Set it on a table, tap the desk, and watch the ground move. You will be surprised how sensitive your phone is. It has been doing that since the App Store opened in 2008, when it reached #1 in Education in Japan, Austria, Finland, and Greece. Version 1.7 is a complete rebuild: faster, clearer, and finally a real instrument. LIVE SEISMOGRAPH • Three axes at up to 100 samples per second, drawn like a strip-chart recorder • Scroll back through up to an hour of history while it keeps recording • Gravity filter with a real corner frequency, so slow tilt disappears and earthquakes stay • Live spectrum: see the frequency of footsteps, a washing machine, or a passing truck at a glance • Dark mode and a full iPad layout EVENT DETECTION • A seismologist's STA/LTA trigger flags every tremor with its peak acceleration, duration, and dominant frequency • Three sensitivity levels, from "only real shakes" to "every footstep" • Events are shaded on the traces and listed so you can jump straight to them RECORDINGS • Every session is saved automatically as compact raw data, split into hourly files • Browse by day, open any recording, scrub to its events, and see its spectrum • Export CSV, or pick up the raw files in the Files app and in Finder • Keep them for a day, a week, a month, or forever WAS THAT AN EARTHQUAKE? • Live USGS feed on a globe, filtered by time window and magnitude • Tap a quake for its depth, time, and the official USGS page STREAM TO YOUR MAC • Open iSeismometer on a Mac on the same Wi-Fi and your phone finds it by itself • The Mac shows every device streaming to it side by side, with its own recordings and event detection • Reconnects on its own after the screen locks, the network drops, or the Mac restarts Made for fun and for learning. A phone carries a MEMS accelerometer, not a broadband seismometer, so it feels footsteps and trucks far better than distant earthquakes. Put it on a solid floor, plug it in, keep the screen awake, and you have a home seismic station. iSeismometer is not a substitute for official earthquake early warnings or emergency alerts. Questions and ideas: info@objectgraph.com "This is a novelty app but one that also helps you learn something new... one of those things that is very captivating once you've looked at it once." — The Independent Guide to the iPhone 3GS