A summary about Earthquake Swarm effecting on a frame as ~5 km x30 km developing as SW-NE between March 28-Apr 5

An earthquake swarm occurred on Iceland's Reykjanes Peninsula in the past days. Within 48 hours, mostly during 3-4 April, 226 tremors were registered around the Sýlingarfell hill in an area near the famous Blue Lagoon about 5 km north of Grindavik and close to the recent eruption site of Fagradalsfjall volcano.

Most quakes were small; only two had magnitudes above 3.0, the strongest being a magnitude 3.3 tremor. However, the depth of the quakes was shallow, clustered around 5 km, and a likely cause of the quakes could be a (small) magma intrusion event at this depth. If this is the case, it should also show as ground uplift in tandem with the quakes, but there have not been any data published on this yet. In the meanwhile, it remains a likely scenario.
In recent years, several smaller and larger earthquake swarms have occurred on the Reykjanes peninsula. Almost all of them had involved significant ground uplift, suggesting that magma intrusions were the cause. The series of earthquake swarms in the past years eventually culminated in last year's volcanic eruption near Fagradalsfjall. Based on historical and geological records, it appears that eruptions on the Reykjanes peninsula typically come as series of several eruptions in close succession at adjacent areas along the rift zone to form clusters spaced apart by longer quiet intervals of the order of approx. 1000 years. After an intense period of eruptions approx. 900 years ago and a following quiet interval until 2021, the newest period of eruptions on the peninsula might have been started with last year's Fagradalsfjall eruption. Thus, many scientists believe that similar eruptions are likely to occur on the Reykjanes Peninsula in the next years and decades. The latest swarm of quakes might just be one of its precursors.