(i) at least two detection units that each have a tremor sensor for detecting tremor signals and an electronic signal processing means for processing and analyzing the tremor signals, in each instance, wherein the signal processing means of each detection unit is configured to detect primary waves of earthquakes on the basis of a signal received from the tremor sensor and to calculate characteristic variables from detected primary waves and compare the calculated characteristic variables with threshold values, the characteristic variables being a measure of the destructive effect of subsequent secondary waves;

(ii) an electronic data bus operatively connecting the detection units with one another, wherein the detection units communicate with one another in master/slave mode, by way of the data bus, such that a detection unit being operated in master mode periodically queries the detection units being operated in slave mode; and

(iii) an alarm configured for activation as a function of the result of the comparison between the characteristic variables and the threshold values,

wherein the detection unit operated in master mode is configured to activate the alarm only if the signal processing means of at least two detection units detect a primary wave, with time correlation.