continued working on tutorial

README.md

@@ -38,8 +38,9 @@ ls
 ```
 
 To get a quick overview on the dataset, use the 
-[Snuffler](http://emolch.github.io/pyrocko/v0.3/snuffler_tutorial.html) 
-application which is part of [Pyrocko](http://emolch.github.io/pyrocko/).
+[Snuffler](http://emolch.github.io/pyrocko/current/snuffler.html) 
+application which is part of [Pyrocko](http://emolch.github.io/pyrocko/)
+([tutorial](http://http://emolch.github.io/pyrocko/current/snuffler_tutorial.html)).
 
 ```bash
 snuffler --stations=stations.txt --events=confirmed-events.txt data/
@@ -156,3 +157,33 @@ detector_threshold: 100.0
 ## Output filename for detections
 detections_path: 'detections.txt'
 ```
+
+An example event from the dataset is shown here:
+
+![example waveforms](doc/gx/alentejo-event1.png "'Event 1' from 'confirmed-events.txt'")
+
+Typical regional, shallow earthquakes appear in this dataset as clear P and S
+coda wave packets travelling with characteristic speeds, packet durations and
+frequency content through the network. To detect such events automatically, we
+can compose an image function with two contributions, one for each dominant
+phase. Such image function contributions (IFCs) can be defined under the
+`image_function_contributions` key in Lassie's configuration [TODO: to be
+renamed]. Different types of IFCs are available and can be combined. Here, we
+use the `WavePacketIFC` which applies a normalized envelope based
+pre-processing to the waveforms before travel-time compensated stacking.
+
+#### Running the detector
+
+To test the configuration, select a short processing time span around one of
+the known events in the dataset. The time span can be restricted with the
+`tmin` and `tmax` entries in Lassie's configuration or with corresponding
+command line options `--tmin='YYYY-MM-DD HH:MM:SS'` and `--tmax='YYYY-MM-DD
+HH:MM:SS.XXX'` [TODO: to be implemented], which override configuration
+settings.
+
+Now run the detector with 
+
+```bash
+lassie scan config.yaml
+```
+