How to Read the AFAD and Kandilli Earthquake Lists

By Nesim Razon, independent Android developer

A list of recent earthquakes is full of small numbers, and it is easy to read them wrongly. This guide goes through one row of the Son Depremler list piece by piece, explains the two sources behind it, the filters, the map and the statistics screen, and shows why AFAD and Kandilli do not always agree. It also says plainly what such a list is not.

Reading one row of the list

Every row is one recorded earthquake. On the left is a colored square with the magnitude, for example 3.4. In the middle is the place name in bold, then, in smaller type, a second line with extra place information, and below it how long ago the earthquake happened together with its depth in kilometers. On the right is the time: just the hour and minute if it happened today, or the date and time if it was earlier.

The time shown is converted to your phone's time zone, so you do not need to calculate anything yourself. The list is sorted with the newest earthquake first. Tap any row to open its detail screen.

What the colors mean

The colored square gives you a quick feel for the whole list before you read a single number. The app uses four colors:

• Green: magnitude below 3.
• Yellow: 3 up to below 4.
• Orange: 4 up to below 5.
• Red: 5 and above.

The same colors are used on the map and in the statistics. They only sort earthquakes by magnitude. They say nothing about whether anyone felt the earthquake or whether anything was damaged.

Two sources: AFAD and Kandilli

At the top of the list a switch lets you choose between AFAD and Kandilli. AFAD is Turkey's Disaster and Emergency Management Authority, and the app reads its public earthquake service. Kandilli is the Kandilli Observatory and Earthquake Research Institute at Boğaziçi University, and the app reads its public list of recent earthquakes. The app is not affiliated with either institution, and the data comes straight from them.

The two sources describe places differently. AFAD gives the province, the district and the neighborhood, so a row can read like a district and province name, with the neighborhood or a sea and distance note underneath. Kandilli gives a single place name for each event. The sources also differ in reach: Kandilli publishes only its latest 500 earthquakes, which is about a week, while AFAD can show a longer period. When you choose Kandilli with a range longer than 24 hours, the app shows a short note about this limit.

The time range and magnitude filters

Below the source switch are two rows of chips. The first row sets the time range: 24 hours, 7 days or 30 days. The second row sets the minimum magnitude: all, 2+, 3+, 4+ or 5+. A magnitude filter shows earthquakes of that value and above, so 3+ includes 4 and 5 as well. The counter above the list tells you how many earthquakes match your current choice.

Your last choices are remembered, so the app opens with the same list next time. To refresh, pull the list down. If the connection fails, the app shows a message and keeps the list it already has. If nothing matches your filters, you will see that there are no earthquakes for this filter, which is a result and not an error. Widening the range or lowering the magnitude is the usual fix.

The detail screen

Opening a row shows a small map with the location at the top, a larger magnitude badge, the place name and how long ago it happened. Below that is a card with five lines: magnitude with its type in brackets, depth in kilometers, the full date and time, the coordinates and the source. Two buttons at the bottom let you share the earthquake as text, including its source, or open the location in your maps app.

Pay attention to the type in brackets after the magnitude. It tells you which kind of magnitude you are looking at, such as ML, Mw or MD, and the same earthquake can carry a different type in the two sources. For Kandilli, the app shows the ML value when it exists, and otherwise Mw and then MD.

The overview map and the statistics screen

The map icon at the top opens a map of all the earthquakes in your current list. Each earthquake is a dot colored by magnitude. Tap a dot to see a small card with its magnitude, place and time, and tap the card to open the detail screen. The map draws at most the latest 1000 earthquakes, and a label tells you when there were more.

The statistics icon opens a summary of the same filtered list. It shows the total number, the strongest earthquake, a bar chart and a breakdown by magnitude. The bar chart counts earthquakes per hour when you choose 24 hours and per day for longer ranges. Tap a bar for details. The breakdown uses the bands below 2, 2 to 3, 3 to 4, 4 to 5 and 5 and above. Because statistics follow your filters, changing the source, range or magnitude changes every number.

Why the two institutes can differ

It is normal for AFAD and Kandilli to show slightly different values for the same earthquake. Each institute uses its own stations and methods, may report a different magnitude type, and may publish at a different stage of review. A difference of a few tenths does not mean that one of them is wrong. If two entries are close in time and place, they are almost certainly the same event.

Numbers can also change after the first publication. The first solution is often computed quickly, and the institutes can revise location, depth and magnitude afterward. A list you open a day later can therefore differ from what you saw first. In Kandilli's own list, each line even carries a note showing whether it is preliminary or revised. For a more detailed explanation, read our article Where Does Earthquake Data Come From? AFAD, Kandilli, USGS. To see how magnitude differs from what people feel, read Earthquake Magnitude vs Intensity: What Is the Difference?

What the app is not

Son Depremler lists earthquakes that have already been recorded. It is not an early warning system. Data reach the institutes minutes after an earthquake, and the app can only show them after that. It does not predict earthquakes, it does not give safety instructions, and it is not affiliated with AFAD or Kandilli. The app needs no location permission and no account.

For official information and alerts, follow AFAD. Use the list to see what happened, to compare the two sources and to follow the small earthquakes in your region. The app is available for Android and iPhone, and it works in Turkish and English.