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Southern California Earthquake Data Center

Earthquake Information

1996 Monthly Seismicity




January 1996 MAP GRAPH
    By far the largest earthquake, and the seismic highlight of January 1996, was a magnitude 5.2 aftershock which struck the Ridgecrest area on the 7th. It produced two immediate aftershocks over magnitude 4, both on the 8th of the month. Another sizable aftershock (M 4.2) struck the same area of the 26th. Not surprisingly, the Ridgecrest sequence kept the rate of earthquakes considerably high this month -- over 2360 earthquakes can be seen here, and at least 1300 of those are Ridgecrest aftershocks.

February 1996 MAP GRAPH
    February 1996 was a month of many earthquakes, but one lacking in large events. Of course, roughly one-third of the nearly 1600 earthquakes recorded in this area over these 29 days were Ridgecrest aftershocks, none of which exceeded magnitude 2.7. The largest quake in the area was M 3.8 Landers aftershock north of Yucca Valley on the February 21. Some interest was generated by each of two smaller quakes felt in populated areas -- a M 2.9 along a thrust fault deep under Compton on the 17th, and a M 3.3 near Fontana on the 24th.

March 1996 MAP GRAPH
    The largest event in March 1996 was a magnitude 4.1 Northridge aftershock on the 19th. This quake had the distinction of being the 50th Northridge aftershock measuring between magnitude 4.0 and 4.9. Starting on March 17, and unfortunately just north of the map area (a few are visible), is a swarm of small events near the place where the Coso earthquake strikes, eight months later. This swarm is about 20 miles north of the Ridgecrest activity. That sequence contributed roughly 480 aftershocks in March, bringing this area's count to over 1490 earthquakes shown here.

April 1996 MAP GRAPH
    Although the seismicity rate for April 1996 was moderately high, the month was a fairly dull one, in terms of large quakes and media attention. The largest earthquake was a magnitude 3.9 Landers aftershock on April 8. While the number of Ridgecrest aftershocks fell to about 300 this month, that was still enough to boost the total count to over 1400 earthquakes in this area.

May 1996 MAP GRAPH
    May 1996 was a fairly interesting month, with most of the excitement focused in the Los Angeles area. While the largest event of the month, a M 4.1 Northridge aftershock on May 1, drew plenty of notice, probably the biggest flurry of interest was sparked on May 23, when a thrust fault almost directly beneath downtown L.A. moved in a magnitude 3.5 earthquake. Also this month, watch for continued activity in the Ridgecrest area (a total of about 250 events), as well as a swarm on the southeastern edge of the Salton Sea in the latter half of the month. In all, over 1220 earthquakes were recorded this month.

June 1996 MAP GRAPH
    It is rare to have an entire month go by without a single quake greater than magnitude 3.2 in this part of California (and northern Mexico), but that is exactly what happened during June 1996. Though over 1150 earthquakes are shown in this animation, the three largest are all magnitude 3.2 -- one near Barstow on the 6th, one near Cajon Pass on the 12th, and one near the Salton Sea on the 20th.

July 1996 MAP GRAPH
    Seismic activity slowed down appreciably in July 1996, with only about 920 earthquakes recorded here that month. Some, but not all, of this drop was due to a lightening of the activity in the Ridgecrest area. The largest events in the animation area this month were three magnitude 3.4 quakes -- one in the San Gorgonio Pass area on the 21st, and two Landers aftershocks near Joshua Tree National Monument, on the 4th and the 28th.

August 1996 MAP GRAPH
    The seismicity rate jumped back up in August 1996, after the previous month's somewhat sluggish pace. Not only were there more events (roughly 1130 earthquakes are shown here), but the strongest were more energetic. There two largest events were a magnitude 4.3 near the Pisgah fault on the 13th, and a magnitude 4.0 which shook the area south of Mexicali on the 29th. The Pisgah event was considered an aftershock of the 1992 Landers earthquake, even though the area it struck had been reasonably quiet since 1992.

September 1996 MAP GRAPH
    The seismicity rate increased again in September 1996, with over 1270 earthquakes recorded. The largest was a magnitude 3.8 on the 12th of the month, located near the town of San Jacinto, along the San Jacinto fault zone. Finishing a close second was a September 10 Ridgecrest aftershock measuring magnitude 3.7. Watch for a somewhat unusual quake -- near San Luis Obispo (by the southern end of the Rinconada fault zone) -- on the 29th.

October 1996 MAP GRAPH
    The largest earthquake of October 1996 was a magnitude 4.2 near Ojai (east of Santa Barbara) on the 23rd, which produced a small aftershock sequence. Also notable was a magnitude 4.1 which struck the area near the Pisgah fault on the 19th. Like the event in August, this was considered a Landers aftershock. The seismicity rate for this area fell somewhat from the previous month, as 1070 earthquakes were recorded during these 31 days.

November 1996 MAP GRAPH
    The largest event shown in this animation of southern California for November 1996 is a magnitude 4.1 Landers aftershock on the 26th, near the site of the 1992 Joshua Tree earthquake. Unfortunately, the seismic "event of the month" occurred just north of the animation area, on the 27th. This was the Coso mainshock, a magnitude 5.3 quake. Though the area covered in the animation experienced only about 860 earthquakes in November 1996, if you added those earthquakes that occurred within just 10 minutes of latitude north of the map, and after the Coso mainshock (just 4 days of this month) you would count over 650 more, every one a Coso event.

December 1996 MAP GRAPH
    December 1996 appears to be a lackluster month for seismicity in southern California. Roughly 890 earthquakes can be seen in the 31 days of this animation, the largest, a magnitude 3.7 event, happened on the 24th, near the White Wolf fault. However, just north of the map area, the Coso earthquake sequence was still very active. Indeed, if the northern boundary of the map were extended just 10 minutes of latitude (to 36°10' N), there would be over 1100 more events plotted in this animation, and practically every one would be part of the Coso sequence.
End of Year 1996 Summary MAP GRAPH



RELATED INFORMATION

Division of Geological and Planetary Sciences | California Institute of Technology