Q:

What are the warning signs of an earthquake?

A:

A fault line may send out tiny shocks, called foreshocks, days or even weeks before a major earthquake. When a fault line is about to rupture and cause an earthquake, the types of waves it sends out change.

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Full Answer

Rupturing faults send out two different types of waves: P-waves and S-waves. The P-waves move faster, but the S-waves are the ones that cause the heavy damage -- along with the waves that move along the Earth's surface. Faults do not send out waves continuously, but once the rupture begins, earthquake sensors can pick up on incoming waves, and alert center staff have time to provide detailed warnings about the coming earthquakes.

The sensors are embedded in the ground, and when the P-waves hit, alert signals go to the center. While these systems provide only minutes or seconds of warning time, often that is enough to allow for the evacuation of major buildings if the quake is a major one. People living in earthquake-sensitive areas often have apps on their phones designed to receive these alerts, so they can prepare for the intensity of the earthquake at their location.

An earthquake early warning system called ShakeAlert was tested in California in January of 2012. ShakeAlert is able to transmit messages almost instantaneously, and may be able to save lives.

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Related Questions

  • Q:

    How does an earthquake form?

    A:

    Earthquakes happen when the boundaries of the Earth's tectonic plates bump and slide past one another; sometimes, they get stuck on jagged edges and cause earthquakes once they are released. These earthquakes are always followed by aftershocks starting from the same epicenter.

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  • Q:

    How do you prepare for an earthquake?

    A:

    To prepare for an earthquake, prepare your house by placing objects to minimize falling damage. Draft an emergency plan, and practice earthquake drills. During an earthquake, drop to your hands and knees, cover your head and neck, and hold on.

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  • Q:

    Where should you hide during an earthquake?

    A:

    The best place to take shelter during an earthquake is underneath a sturdy desk or table, preferably one that covers the entire body. If this option is not available, protecting the head and neck is the most important safety concern. Do not stand in a doorway, as that advice is outdated and unsafe.

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  • Q:

    When was the first earthquake?

    A:

    The first earthquake to ever take place is unknown as it happened before the records of the events were kept. The first recorded earthquake was in 1769.

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