- I’m listening on my laptop (or iPhone, iPad, etc.), but I’m really not hearing much. What’s going on?
- Many of the sounds in these recordings contain low frequencies that aren’t reproduced well by the speakers in these devices. Try using earbuds or headphones. Better yet, plug your machine into a good sound system.
- At what time of day does each recording start?
- Each recording begins just after midnight UTC (Coordinated Universal Time, or Greenwich Mean Time) of the first day and runs through midnight UTC of the last day. For example, the program for the week of March 16-22 begins at exactly 00:00 March 16 UTC (8pm Saturday March 15 EDT here in Maine) and runs until just before midnight March 23 UTC (8pm Saturday March 22 EDT). To convert from UTC to your local time zone, see www.timeanddate.com.
- How did you get these stereo recordings from a single seismometer?
- As a seismic wave travels through the solid Earth, each tiny particle of rock in its path moves in a complicated three-dimensional trajectory. The seismometer independently captures all three components of this motion as the wave passes by: up/down, north/south, and east/west. By carefully combining these three components into a two-channel audio mix, it’s possible to create a satisfying stereophonic effect. (Even more interesting effects are possible with multiple loudspeakers — but that’s another story…)
- How do you know where and how big the earthquakes were?
- A huge global network of research seismometers — run by governments, universities, and combinations thereof — constantly monitors the Earth’s seismic vibrations. When an event is detected, automated (i.e., computer-based) and human analysts swing into action, calculating the location and magnitude of the earthquakes using well-understood principles of seismology. Online catalogs of seismic events are updated quickly (see, for example, IRIS’s “Seismic Monitor”, which shows a colorful near-real-time map of earthquakes happening around the world).
Each week, I compare my recordings against IRIS’s list of identified seismic events. It’s usually quite clear which sounds correlate with which events. Occasionally, however, I detect events that do not show up on the IRIS catalogs. Many of these — particularly small earthquakes in the Northeastern US — do appear in the USGS catalog. Those that don’t appear in the USGS catalog are probably nearby events (blasting, etc.) that are too small to be detected by other stations. Some sounds defy explanation.
- More questions? Please post your queries below.