iTemblor
Welcome to the iTemblor Support Page for the iPhone and iPod Touch
To learn about iTemblor, select a topic:
Choose one of the views which shows motion in the horizontal plane:
1. Earthquake Magnitude (Mag.)
2. Modified Mercalli Intensity (MMI)
3. Percentage of Gravity (% g)
To use iTemblor, hold your iPhone horizontally and shake in a steady, rythmic motion. Shake harder to register higher values. For best results, you can place your iPhone on a flat surface and slide it back and forth or shake the surface to simulate an earthquake. iTemblor will continuously display the last five seconds of recorded data.
Notice how sensitive iTemblor is when you shake lightly. This is due to the fact that small differences in acceleration amplitudes will translate to large differences in earthquake size or intensity at lower acceleration values.
On the display, the green circle indicates the most recent acceleration recorded while the red circle marks the maximum acceleration and numerical value recorded during the session.
Use the Clear button to clear the current session. The Pause button will stop the recording so that you can study it. Tap Resume to continue where you left off.
The Seismograph button will flip the page and display the three direction time history of your shaking in percentage of gravity (%g) along the x, y, and z axes. Unlike the prior views which work best held horizontally, the seismograph view can be rotated any way you like!. Tap Seismoscope to return.
The Seismograph view displays two time series per axis. The Yellow time history is the raw, unfiltered reading from your onboard iPhone accelerometer. The Orange trend represents the filtered raw time history which is used to calculate the results presented by iTemblor.
Filtering the raw data is required to ensure consistency with the seismological relationships used in iTemblor. It´s interesting to observe the difference between signals when gravity and high frequency motion has been eliminated!
Like most iPhone applications, iTemblor does not close until you press the Home button, so you can leave it on and see what it records. Maybe you can record a real earthquake! You can also have it on when you walk around or ride a bicycle and see what kind of “g” forces your body records in everyday life.
iTemblor was designed to provide interesting correlations between the accelerations you impart on your iPhone through shaking and earthquake magnitude and intensity. Empirical seismological relationships which approximate these correlations are used in iTemblor.
Have fun and remember to shake safely!
iTemblor translates your iPhone acceleration values into Richter earthquake magnitudes and plots them in the range of M5 to M9.
Earthquake magnitudes are typically determined from mechanical recordings on seismographs which record the actual physical ground motion due to earthquakes.
While people are very familiar with earthquake magnitude values, they are often misunderstood because they are logarithmic scales, which means that a magnitude 4 earthquake is not twice as strong as a magnitude 2 earthquake!
It´s good to remember that a 1 unit increase in the earthquake magnitude scale translates to a 10 times increase in the amplitude of the ground motion being recorded.
In terms of energy release, a 1 unit increase in the earthquake magnitude scale corresponds to an approximate 32 times increase in energy release!
For a list of the worlds largest earthquakes ever visit:
iTemblor also translates your iPhone accelerations into shaking intensity as measured by the Modified Mercalli Intensity (MMI) scale. The MMI scale possesses values from I to XII while iTemblor plots MMI values from VI to XII.
Earthquake intensity scales like MMI are very different from earthquake magnitude scales because they are based on direct observation by people rather than recorded by instruments.
The MMI scale is therefore very important because it allows seismologists to map earthquake effects to regions where seismographic instruments are not present.
As you will see from its description, MMI is a scale to which non-scientific people can readily understand and relate.
| MMI | Severity | Description |
|---|---|---|
| I | Not felt. Marginal and long period effects of large earthquakes. | |
| II | Felt by persons at rest, on upper floors, or favorably placed. | |
| III | Felt indoors. Hanging objects swing. Vibration like passing of light trucks. Duration estimated. May not be recognized as an earthquake. | |
| IV | Hanging objects swing. Vibration like passing of heavy trucks; or sensation of a jolt like a heavy ball striking the walls. Standing motor cars rock. Windows, dishes, doors rattle. Glasses clink. Crockery clashes. In the upper range of IV, wooden walls and frame creak. | |
| V | Light | Felt outdoors; direction estimated. Sleepers wakened. Liquids disturbed, some spilled. Small unstable objects displaced or upset. Doors swing, close, open. Shutters, pictures move. Pendulum clocks stop, start, change rate. |
| VI | Moderate | Felt by all. Many frightened and run outdoors. Persons walk unsteadily. Windows, dishes, glassware broken. Knickknacks, books, etc., off shelves. Pictures off walls. Furniture moved or overturned. Weak plaster and masonry D cracked. Small bells ring (church, school). Trees, bushes shaken (visibly, or heard to rustle). |
| VII | Strong | Difficult to stand. Noticed by drivers of motor cars. Hanging objects quiver. Furniture broken. Damage to masonry D, including cracks. Weak chimneys broken at roof line. Fall of plaster, loose bricks, stones, tiles, cornices (also unbraced parapets and architectural ornaments). Some cracks in masonry C. Waves on ponds; water turbid with mud. Small slides and caving in along sand or gravel banks. Large bells ring. Concrete irrigation ditches damaged. |
| VIII | Very Strong | Steering of motor cars affected. Damage to masonry C; partial collapse. Some damage to masonry B; none to masonry A. Fall of stucco and some masonry walls. Twisting, fall of chimneys, factory stacks, monuments, towers, elevated tanks. Frame houses moved on foundations if not bolted down; loose panel walls thrown out. Decayed piling broken off. Branches broken from trees. Changes in flow or temperature of springs and wells. Cracks in wet ground and on steep slopes. |
| IX | Violent | General panic. Masonry D destroyed; masonry C heavily damaged, sometimes with complete collapse; masonry B seriously damaged. (General damage to foundations.) Frame structures, if not bolted, shifted off foundations. Frames racked. Serious damage to reservoirs. Underground pipes broken. Conspicuous cracks in ground. In alluvial areas sand and mud ejected, earthquake fountains, sand craters. |
| X | Very Violent | Most masonry and frame structures destroyed with their foundations. Some well-built wooden structures and bridges destroyed. Serious damage to dams, dikes, embankments. Large landslides. Water thrown on banks of canals, rivers, lakes, etc. Sand and mud shifted horizontally on beaches and flat land. Rails bent slightly. |
| XI | Rails bent greatly. Underground pipelines completely out of service. | |
| XII | Damage nearly total. Large rock masses displaced. Lines of sight and level distorted. Objects thrown into the air. |
Masonry A: Good workmanship, mortar, and design; reinforced, especially laterally, and bound together by using steel, concrete, etc.; designed to resist lateral forces.
Masonry B: Good workmanship and mortar; reinforced, but not designed in detail to resist lateral forces.
Masonry C: Ordinary workmanship and mortar; no extreme weaknesses like failing to tie in at corners, but neither reinforced nor designed against horizontal forces.
Masonry D: Weak materials, such as adobe; poor mortar; low standards of workmanship; weak horizontally.
For more information on intensity scales visit:
The seismological relationships used in iTemblor and the MMI scale descriptions are taken from:
Elementary Seismology by Charles F. Richter, Freeman and Company, 1958.
For more information about earthquakes and earthquake safety visit:
December 26th, 2008 at 14:02
Very nice program. I put it in my list of educational iPhone software under Geography:
http://web.me.com/planeten.paultje/Toepassingen/iPhone.html