• Mariya Galochkina

A Week of Earthquake Location + A Real Earthquake

This has been a very earthquake-oriented week. Jesus and I spent most of the week at ICE, working on picking first arrivals of P and S waves and magnitudes from the 390 possible seismic events from the month of April in order to locate earthquakes.

One of the waveforms I picked this last week. I chose the 3 events with the earliest P wave arrivals (which are always picked from the Z channel, which detects up and down motion), and picked the S waves from the other channels.

We also learned how to make focal mechanisms using Seisan, which will come in handy for Jesus's project in particular. A focal mechanism is a visual model of the deformation that took place in a particular seismic event, and enables seismologists and geologists to get a better idea of the orientation of the faults along which earthquakes take place. Jesus's project will involve creating focal mechanisms for many of the earthquakes from recent years in order to locate and study the major faults along which many of the earthquakes take place.

An example focal mechanism from the Seisan tutorial (My laptop is having some issues making focal mechanisms, but I hope to fix that soon)

Overall, I'm starting to get the hang of picking P- and S-wave arrivals, and I'm eager to take on finishing the rest of the events that were assigned to us.

This week, Jesus and I also got a better idea of the roles RSN and the seismology department of ICE play in earthquake detection. Krista gave us an in-depth explanation of the process of how ICE monitors earthquakes as well as the installation, maintenance, data retrieval, and data processing that they undertake. We got a detailed picture of the work ICE does as well as what they hope to improve in the upcoming year.

Yesterday, we got exceptionally lucky. While we were sitting and working in the RSN lab, we felt our first large earthquake of the trip (there had been a smaller one earlier in the morning, but I wasn't sure if I felt it).

The earthquake, as recorded on the RSN's screen of live seismic data transmission.

The irony of experiencing the largest earthquake of the year while sitting inside the national lab responsible for detecting them and sending out information was not lost on us. We all excitedly watched as Juan Luis, an employee of the RSN, speed-picked first arrivals of the incoming seismic data and sent out the notice with the information of the earthquake. The rest of the afternoon involved us working while the RSN was abuzz with phone calls, journalists, and a lot of rapid-fire science (Jesus and I got to see Dr. Ivonne Arroyo power through almost a hundred waveforms to pick the polarities of the incoming wave in order to make a focal mechanism for the earthquake and locate the faulting motion that had caused it). Being able to see not only the science but also the other important duties that the RSN undertakes in action was extremely fascinating, and it truly gave us a firsthand understanding of the scientific and social importance of the work done at the RSN.

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