ANALYSIS OF SEISMIC NOISE IN THE CITY OF LA PAZ AT THE LIGHT OF THE COVID-19 LOCKDOWN: A COMPARISON WITH THE OCCURRENCE OF HURRICANES

Abstract:

The study of seismic noise has turned out to be a powerful tool to quantify the activity of a city. In the city of La Paz, Baja California Sur, the LPIG seismic station is located at an important place that connects downtown with the urban suburbs.The most important avenue that connects the city center with the highways to the south of the state is located a few meters from the LPIG station. Due to the urban plans this site was also monitored by the authorities. When making an analysis of seismic noise using probability spectral density, the decrease in the level of seismic noise is observed immediately after the promulgation of the lockdown. However, the true cause of the decrease in activity is related to the municipal prohibition of tourist activity. It is interesting to note that the return to noise levels are gradual and not related to the change in traffic light colors of the health alert system. In addition, some changes were presented in the way of calculating the noise values based on a switch-point change for a distribution of a Poisson point process and we see that the data probably reflects the noise level changes better. We compared the noise levels that occur in case of other natural disasters, especially in hurricanes. In the case of hurricanes, home confinement is necessary because temporary streams flood the main avenues, and it is necessary to wait for traffic to be safe in the city, therefore crossing streams is extremely dangerous. We observed that seismic noise is reduced in all the cases. Urban seismic stations are very helpful, we also explored the possibility to use the seismic noise as a tool to quantify tropical cyclones. It is necessary to promote the study of seismic noise for social purposes by supporting the city authorities.