New Jersey earthquake makes waves in Baltimore

Surprised people across the region sensed the tremors, prompting Hopkins affiliates to ask each other, "Did you feel it?" He explains that the top plot shows the vertical ground velocity over time. The larger amplitudes around 14:24 UTC (Universal Time, which is four hours ahead of EDT) indicate high velocities when the earthquake reached Baltimore. The bottom plot also shows velocities, he says, but in what is known as a spectrogram, showing the frequencies, or different pitches, contained within the signal. The bright oranges and yellows indicate higher energies, and dark purples and pinks indicate lower energies, Fernando says.