Ensenada’s Earthquake Zone

[Editor's note: click on the map to turn on interactive features, other faults, zoom, etc.

The Agua Blanca fault(shown passing through the Punta Banda peninsula that is my neighborhood) is a major, trans‐peninsular, right‐lateral fault located in northern Baja California. Its WNW‐ESE orientation is markedly different from the general trend of the San Andreas‐Gulf of California fault system. From a geological point of view, the Agua Blanca fault is considered active, but there has been little significant seismic activity directly associated with it. On October 9, 1981, the onset of an earthquake swarm was detected at the Ensenada seismic station (ENX), with a S‐P time average of 2 sec. Shortly after this, an array of up to seven portable seismic stations was installed by CICESE around Todos Santos Bay. More than 180 events were recorded during the following 10 days, after which the local seismicity decreased. A second swarm consisting of 100 microearthquakes was detected between November 28 and December 5, 1981. The epicentral locations of those events recorded at four or more local stations all lie inside Todos Santos Bay. The composite fault plane solution for both swarms indicates a right‐lateral strike‐slip vertical fault with a strike of N52°W. Geological observations allow us to conclude that the seismic activity reported here is associated with the Agua Blanca fault zone.]

Summary

The interactive Google map on this page shows the most recent earthquakes recorded by the http://eqinfo.ucsd.edu/deployments/anza/”>Anza seismic network. Active stations in the network are plotted as yellow triangles, with the station code underneath. Earthquakes are colored by age from present, and scaled by magnitude (see the legend on the right of the map layer). Clicking the earthquake icon on the map displays a window containing information on the specific event.

Navigation

Move the map around by using the arrow keys in the top left of the map or click and drag the cursor in the map layer. Zoom in and out of the map by using the slider bar, or plus and minus buttons, or your mouse scroll wheel, in the map layer. Reset the map view by clicking the four arrow key in the center of the navigation console in the map layer. If you don’t wish to see the station names displayed, click the checkbox next to the ‘Show station codes’ in the “Event legend” STATIONS section. Click the checkbox again to show the names.

Display fault zones

Interactively show and hide faults in Southern & Central California, and Baja California Norte, Mexico by checking or unchecking the boxes next to each fault name in the “Fault Legend” layer on the left of the map. Fault traces are displayed in dark red. Clicking one of the region names in the Fault Legend layer will display a list of all the faults that can be shown in that region. A check box next to the fault name can be clicked to display a fault trace directly on the map layer. Clicking the trace will open a bubble window displaying the name of the selected fault zone. Note: Fault resolution drops off at ˜ 30ft.

Modify the time range plotted

You can modify the time range of earthquakes plotted by moving the slider bar located in the top right of the map layer and clicking the “Replot” button.

Draggable layers

If the “Fault Legend” and “Event legend” layers are obscuring a feature of interest to you, they can be dragged around the map by clicking on the directional arrow in the top-right of the layer.

Warning

Turning on all the faults and dragging the map takes a lot of web browser processing memory. It is highly recommended that you use this page only if you have a broadband connection to the internet.

source

Editor: this April 2012 article take a look at increased activity in the Pacific ring of fire in recent years.

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