**3. Event detection, visualization, and archiving**

The PGV map as shown in **Figure 3** is transient. Significant seismic events should be detected and saved in order to keep this information and to make it available for more detailed analysis. The definition of a seismic event and proper trigger criteria should take the data quality into consideration. MSS stations are intentionally mounted in buildings where people potentially experience ground motions and report their observations. These places are frequently noisy and even high PGVs may be recorded due to nearby activities (e.g. traffic, construction work, washing machine, etc.). The main objective of a detection algorithm is to distinguish high amplitude noise at individual stations and regional events like earthquakes or quarry blasts. We perform a "Delaunay" triangulation [7] of the MSS station network and examine the triples of PGV values belonging to the different triangles. Once the minimum PGV value within one triple exceeds a preselected threshold the recorded PGV at all MSS-stations are classified as a seismic event. The duration of the seismic event is expanded by the triggering of other Delaunay triangles and prolongated by a listening time window. This time window takes care of the propagation of the maximum amplitude seismic waves over the network area. **Figure 4** shows the temporal sequence of the trigger status for an entire seismic event.

As soon as a seismic event ends, the seismic data of the respective time window is archived. We offer two options for the visualization of the whole seismic event:


Both visualizations are available in NRT after the seismic event.

The PGV values observed during an earthquake are strongly affected by specific geological and technical peculiarities at the individual MSS stations. In the Section 5.1 we introduce station amplification factors "SA" to improves the fit of PGV to a power law amplitude - distance relation. The application of SA significantly improve the spatial correlation of PGV. Contours become much smoother and better delineate the areas of felt ground motions and maximum shaking. Therefore, we also offer the aforementioned data display alternatively based on PGV/SA instead of PGV (**Figure 5c, d**).

Beside the maximum PGV values of each event and the visualization options, the archive also provides quick and easy access to the PGV-time series and the original seismic traces (MSEED, 100 Hz). Interactive data analysis by seismologists and

Since the beginning of MSS recording, the macroseismic intensities of 16 earthquakes in the area of the MSS-network were evaluated according to EMS-98 by the Seismological Service of ZAMG. These intensities were assigned to macroseismic data points corresponding to municipalities. We relate each macroseismic data point to PGV values recorded within a circumference of 5 km. In total 120, PGV

The maximum epicentral intensity V was assigned for a magnitude ML = 3.7 earthquake with PGV up to 8.44 mm/s. The minimum PGV associated with intensity ≥ II amounted PGV = 0.05 mm/s. On the other hand, we observed PGV values up to 0.42 mm/s related to earthquakes with no reports about felt ground shaking. The number of PGV values, binned to PGV classes, is opposed for 'felt' and 'not felt' in **Figure 6a**. The number for 'felt' overtakes 'not felt' from the class 0.03–0.1 mm/s to the class 0.1–0.3 mm/s. As a first estimate, we set PGV = 0.1 mm/s as the lower valueof felt earthquakes in exceptional instances (higher floors, night time, at rest,

**Figure 6b** shows the cross plot of intensity over PGV. The scatter of PGV within intensity classes is considerable and exceeds, in part one decade. Preliminarily we

The estimate of macroseismic intensity from instrumental data and vice versa is an important issue for the preparation of shake maps (e.g., https://earthquake.usgs. gov/data/shakemap/). These maps provide just in time information about the area and magnitude of ground shaking of an earthquake and its effect on human perception as well as the intactness of infrastructure derived from instrumental observatory data. In principle, we attempt the same procedure with our PGV contour maps. However, the correlations implemented worldwide differ significantly from our relation (e.g., [9]). The attenuation relation used by the Swiss Seismological

*(a) Frequency of PGV values of 'not felt' versus 'felt' earthquakes recorded at MSS stations between October 2017 and October 2020; (b) intensity (EMS-98) over PGV for the same data set; gray line shows a preliminary*

assume a non-linear relation between the logarithm of PGV and intensity. According to the macroseismic detection threshold derived before, the relation is fixed to PGV = 0.1 mm/s at intensity II. The PGV values corresponding to the isoseismals III, IV and V are 0.3 mm/s, 1.0 mm/s, and 10 mm/s. This correlation allows for the interpretation of the corresponding contours in our PGV maps

motivated citizen scientists is supported by this portal.

*DOI: http://dx.doi.org/10.5772/intechopen.95273*

*Seismological Data Acquisition and Analysis within the Scope of Citizen Science*

intensity pairs were found by this procedure.

**4. PGV and intensity**

etc.), or with intensity II.

(**Figure 5d**) as isoseismals.

**Figure 6.**

**43**

*PGV-intensity relation.*

#### **Figure 4.**

*Sequence of visualizations of the trigger status of Delaunay triangles during the ML = 2.5 earthquake near the center of the MSS-network, 14th June 2019.*

#### **Figure 5.**

*Visualization of the ML = 2.5 earthquake near the center of the MSS-network, 14th June 2019; (a) coloring the Voronoi regions according PGV, (b) contouring PGV by Kriging, (c) coloring the Voronoi regions according PGV/SA, (d) contouring PGV/SA by Kriging.*

Beside the maximum PGV values of each event and the visualization options, the archive also provides quick and easy access to the PGV-time series and the original seismic traces (MSEED, 100 Hz). Interactive data analysis by seismologists and motivated citizen scientists is supported by this portal.
