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Earthquakes layer
The Earthquakes layer shows all the earthquakes in recorded history
above a certain magnitude: 3.0 for most states, 4.0 for California.
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| Earthquakes in the San Jose, CA region |
Earthquakes of western Washington state |
Details
Date
The date and time (if available). For old earthquakes, only the year,
or year and month, may be available.
Depth
The depth of the event, if known. This may be qualified by e.g. "restrained by geophysicist" or "questionnable".
Magnitude
The accepted magnitude of the event. This is the USGS's best choice
of all the reported magnitudes.
Intensity
The intensity of the event on the Modified Mercalli Intensity scale.
Effects
Observed effects from the earthquakes
- None : the earthquake had no obvious effect
- Heard : the earthquake was heard
- Felt : the earthquake was felt
- Damage : the earthquake caused some damage to property or animals
- Casualties : the earthquake causes injuries or death to humans
Phenomena
Any phenomena observed during or shortly after the earthquake: tsunami, seiche, liquefaction, geyser, etc...
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Options
Transparency
Determines how much the underlying layer(s) will show through this layer.
Color by
- Intensity : stronger earthquakes will appear more red
- Age : more recent earthquakes will appear more red
- Neither : all earthquakes look the same
Shape
Defines the shape to be used to represent the earthquakes
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Origin
This layer uses the data available from the USGS's Earthquake Hazard Program.
The data was retrieved from the Rectangular Area Search application.
For the period 1568 - 1972, we selected from the Significant U.S. Earthquakes (USHIS) database.
For the period 1973-present, we selected from the Preliminary Determinations of Epicenters (PDE) Monthly Listing.
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