As a simple example consider an earthquake of magnitude 7.5 for which the radius of the area that will experience strong ground shaking is roughly 55km, assuming a point source rupture for simplicity. The S-waves, which mark the onset of the most energetic seismic waves, travel at a speed of about 3.5km/s, and P-waves, which carry the first information about the earthquake, travel at a speed of about 6.5 km/s. For an earthquake that happened at a depth of 10km, a seismometer directly at the epicentre could first detect the earthquake from P-waves around 1.5s after it occurred. At this point, the S-wave arrives only around 1.3s later, with very limited scope to provide advanced warning. The S-waves though will take over 15s to reach a site 55km from the earthquake. Considering operational delays of around 3 s (to collect seismic data from the wider network at the hub, predict the ground shaking, and send the alert), a warning could be issued around 10 s before the onset of strong ground shaking for sites at 55km, though right above the epicentre the warning would be late.
http://www.seismo.ethz.ch/en/research-and-teaching/fields_of_research/earthquake-early-warning/
Depremin ardından ilk önce 6,5 km/saniye hızla P dalgası (Primary) yayılırmış. Ardından 3,5 km/saniye hızla asıl yıkıcı olan S dalgası yayılırmış (Secondary).
26.09.2019 Silivri depreminin merkezi bana yaklaşık 60 km uzaklıktaydı
![](https://i1.wp.com/halimoglu.com/blog/wp-content/uploads/2019/09/deprem2.jpg?fit=625%2C363)
Erken uyarı için 2 senaryo düşündüm:
1. senaryo deprem sensörünü merkeze yakın konulandırırsak, p dalgasını 9 saniye önceden, s dalgasını 17 saniye önceden bilebilecektik.
2. senaryoda deprem sensörü yanıbaşımızda olsa bile p dalgası geldiğinde yani yıkıcı s dalgası gelmeden 8 saniye önce uyarı verebilirdik.
Sensör ile bizim aramızdaki iletim hızı internet üzerinden birkaç milisaniye.
![](https://i0.wp.com/halimoglu.com/blog/wp-content/uploads/2019/09/deprem.png?fit=625%2C255)
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