The corona crisis offers earthquake researchers unimagined opportunities. Due to the weeks-long standstill of many social areas, it has also become quieter on the surface of the earth.
As a result, earthquake signals were easier to detect than before the corona lockdown. "The decrease in ground motion was clearly measurable at many stations," says seismologist joachim ritter of the karlsruhe institute of technology (KIT). With the gradual return to normal life, the earth’s surface is rumbling more and more.
However, the geophysicist hopes that the evaluation of the data from the period of corona silence will yield many new findings for earthquake research. "I hope that we will see signals at a few measuring points that we had not otherwise detected," says the KIT professor.
Researchers believe they are detecting more micro-earthquakes, which are important for predicting larger earthquakes. "Normally, the signals from the small quakes are drowned out," says ritter.
"The earth’s surface is never absolutely still, but constantly in slight motion," explains the geophysicist. This "seismic noise", which cannot be felt by humans, is caused by natural factors such as sea waves and wind, but also by human sources such as traffic, construction work and industry. Heavy trucks, railroads, and wind turbines in particular leave characteristic signals and cause the earth to vibrate.
During the day this ground unrest is stronger than at night, on weekdays more violent than on weekends. Above all, human-induced noise drowns out most earthquake waves – and disturbs researchers. Normally. Since the corona lockdown took effect in mid march, seismologists in germany and europe have recorded "20 to 30 percent fewer noise emissions" on average, according to the KIT scientist. The reduction was particularly noticeable in coarse cities such as milan or stuttgart and on heavily frequented traffic axes. "So little noise is usually only at christmas or easter," says ritter.
Only measuring stations far away from human noise sources were unimpressed by the corona lockdown: at the seismological station of the joint geoscientific observatory of KIT and the university of stuttgart in the schwarzwaldstollen schiltach, for example, there was hardly any decrease in ground motions to be observed. Seismologists have not yet been able to evaluate all of the approximately 300 measuring points nationwide, including more than 50 in baden-wurttemberg. Ritter is certain, however, that the results will provide material for "a number of studies in the coming years".
He is also looking forward to the evaluation of the investigations with mobile stations in the hohenzollern/albstadt area, where the earth has already shaken more frequently. Detection of micro-earthquakes could help map potential future rupture sites – locations of coarser earthquakes.
But even they cannot make a precise prediction: "we can say where there will be a quake and how strong it will be – but not when."Ritter illustrates this as follows: "it’s like a rubber band: i can see the tension building up, but i don’t know how much further the rubber will stretch before it rubs."Earthquake researchers are nevertheless important advisors for politicians: they know where buildings must be constructed to be earthquake-proof and also where it is better not to put a chemical plant.