Nevada has a lot of earthquakes but most happen in uninhabited areas. Rarely do they occur in populated areas but in February, Wells Nevada suffered serious damage from a quake. What would happen if when there was a quake in Las Vegas? Here is an article and an abstract from a Geological Society of America presentation:

PRICE, Jonathan G., ARRITT, Christine, HASTINGS, Jordan T., DEPOLO, Craig M., and HESS, Ronald H., Nevada Bureau Mines & Geology, University of Nevada, Reno, MS 178, Reno, NV 89557-0178, jprice@unr.edu

Earthquake risks in southern Nevada are huge. Quaternary faults, including several in and near Las Vegas Valley, occur within damage distance to nearly every community within the region. Both normal and strike-slip faults are present, and basin effects may accentuate ground shaking. Using the loss-estimation model developed by the Federal Emergency Management Agency on scenarios representative of earthquakes that have occurred in the geological past, a magnitude 6.6 earthquake near Las Vegas today could cause up to $18 billion in building-related economic loss and up to 900 fatalities. Approximately 30,000 buildings may suffer major damage, and up to 11,000 people may need public shelter. Police and fire stations may be operating at 50% functionality, and local hospital beds may be available for fewer than 50% of the people requiring care. According to the U.S. Geological Survey’s probabilistic seismic hazard analysis, the probability of such an earthquake occurring within the next 50 years within 50 km of Las Vegas is less than 5%, but the probability of a magnitude 6.0 or greater earthquake occurring in the same area and timeframe is between 10 and 20%. Even a magnitude 5.9 earthquake on the Frenchman Mountain fault could cause up to $9 billion in building-related economic loss and up to 300 fatalities. The earthquake hazards for Las Vegas and Pahrump, NV are comparable to those for Fresno, CA, Albuquerque, NM, and Portland, OR, while the hazards for Beatty, NV are comparable to those for Salt Lake City, UT. The communities of Pioche and Laughlin appear to have lower hazards and risks than other southern Nevada towns. The risks can be lowered through structural and non-structural mitigation and by avoiding building across faults or in landslide- and liquefaction-prone areas.

This is why we don’t have shelves over the kid’s beds, keep flashlights handy and take other precautions. You should do the same and be prepared to survive on your own for several days without help. Las Vegas is very isolated from other population centers and it could take help from other cities a long time to arrive.