Final answer:
Greg is monitoring his electronic devices to check for alerts about potential aftershocks or tsunamis.
Step-by-step explanation:
Greg is monitoring his electronic devices in this scenario to check for an alert for a potential aftershock or tsunami. As a seismologist, he understands that large earthquakes can trigger aftershocks or tsunamis, so he wants to stay updated with any warnings or alerts that might be issued. Monitoring his phone and e-mail allows him to receive timely information and take appropriate action if necessary.