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There are two problems if one seeks a large, statistically useful sample of seismic events on or around Lombok: (1) there does not seem to be any contemporary data for Richter 4.2 or weaker events and (2) not much history before 1975. The use for weak events today that I doubt anyone can feel is that they would be a good signal for magma movement. Most of the time no one cares about events below Richter 5.0 – the exception is when there is a volcano nearby. Then hundreds or even thousands of Richter 1s and 2s in a short time are a clear warning of an imminent eruption. For example, if there were hundreds of Richter 3s shaking Lombok today that is a profoundly different situation than just a few Richter 3s. The second problem is there are about 40 years of seismic history available. Unfortunately, the quality of most data more than 20 years ago is doubtful. The equations and sensors have not changed much, although Indonesia has improved its hardware in the last 12 years or so. For intermediate strength earthquakes (Richter 5.5 to Richter 7.4) the date, time, Richter and epicenter are useful. The measure of depth was a problem. To be fair, it may be that depth to the nearest 10 kilometers is close enough. For powerful earthquakes (Richter 7.5 or greater) what is really needed besides the epicenter is the geographical extent of major damage. That still is not available today. For weaker earthquakes Richter 4.0 to Richter 5.4 it is not clear that these were always recorded. That is something of a pragmatic measure – they rarely cause significant damage. Below we have Lombok earthquakes 1950-1999 – one Richter 5.8 in 1995 (cayn circle at the top; and that was well offshore) and 8 other Richter 5.0 to Richter 5.4s. That’s just about earthquake-free,  especially by Indonesian standardsLombok_Earthquakes_1950_1999

Then three Richter 5 or greater events – three of which were offshore – in 16 years


Five Richter 4s (zero Richter 5s) in the last three and one half years.Lombok_Earthquakes_2015_2018