Earthquake Commentary for December, 1998

Map of recent earthquake activity

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17:03 PST, Thursday, December 31

We recorded and analysed 219 earthquakes in the past week. Click here to see a summary and map .

17:05 PST, Thursday, December 24

We recorded and analysed 205 earthquakes in the past week. Click here to see a summary and map .

13:24 PST, Tuesday, December 22

Quakes of interest in the last couple of days include: a M2.7 at 11:20 am on Sunday, 12 miles north of Santa Maria; two more quakes located 7 miles south of Newport Beach, M2.8 at 6:18 pm and M2.7 at 7:15 pm on Sunday; a M2.7 at 2:55 pm on Monday, 11 miles east-souteast of Ocotillo; two M2.5's 4 miles northwest of Lake Henshaw, at 7:59 pm and 8:01 pm on Monday; and a M2.9 at 9:29 pm, 7 miles southeast of Anza. Nothing terribly exciting, but quite a few of them.

15:09 PST, Sunday, December 20

Early this morning, a M3.2 and a M3.7 occurred at 6:23 am and 6:25 am. They were both located offshore, 8 miles southwest of Laguna Beach.

22:07 PST, Friday, December 18

We had a tiny swarm at Bombay Beach late this afternoon: a M2.4 at 5:00 pm, a M1.7 at 5:01 pm, a M2.1 at 5:03 pm, and a M2.5 at 5:06 pm. This is the location where the Brawley Seismic Zone joins the San Andreas fault. The focal mechanisms are poorly determined because of the small magnitudes, but they appear to be strike-slip, consistent with either fault system.

12:58 PST, Friday, December 18

There was a M3.9 quake offshore early this morning: 1:38 am, location 11 miles north of Santa Barbara Island. This puts the quake 30 miles south of Pt. Mugu. There were no 'felt' reports.

Another quake possibly big enough to feel was a M2.9 at 4:39 am, located 6 miles west of Mt. San Gorgonio. There has been a sporadic aftershock sequence at that location, from a M4.8 on August 16.

16:18 PST, Thursday, December 17

We recorded and analysed 183 earthquakes in the past week. Click here to see a summary and map .

09:16 PST, Thursday, December 17

The only excitement in our area overnight was a M3.3 at 5:49 pm, located 22 miles north-northwest of Trona. We've had no inquiries.

08:34 PST, Tuesday, December 15

There was a M2.6 Landers aftershock yesterday afternoon at 3:26 pm. The epicenter was 9 miles south of Joshua Tree, and there have been no 'felt' reports.

09:45 PST, Monday, December 14

At 11:39 pm on Saturday, there was a M3.7 quake located 4 miles east-southeast of Ocotillo, near the U.S./Mexico border, with a M2.5 aftershock at 12:11 am Sunday. We did not get any inquiries.

We did have a few inquiries about a M2.5 at 3:09 pm on Sunday, under Inglewood, in the Newport-Inglewood fault zone. We apologize for the error in reporting the magnitude of this event on the phone message; we assume that you all got a thrill out of hearing there was a M6.6 that you didn't feel!

11:53 PST, Saturday, December 12

At 5:02 am today, there was a M2.5 Landers aftershock, 17 miles north of Yucca Valley. This is very sparsely inhabited country, so we do not expect to get inquiries.

Of somewhat more interest was a M3.5 at 7:03 am, 6 miles north of Cabazon, in the foothills of the San Bernardino Mountains. We haven't gotten any public inquires yet, but this quake could easily have been felt.

11:18 PST, Friday, December 11

Beginning last night at 10:03 pm, our quiet seismicity picked up a bit. The first noticable event was a M3.6, at 10:03 pm, located in the mountains 16 miles north-northwest of Tehachapi. There were five aftershocks so far, the largest being M2.5, at 10:54 pm. Probably because of the mountainous terrain, these events escaped notice by the public.

At 12:14 am, there was another M3+, this time a M3.7 located offshore, 21 miles south-southwest of Pt. Arguello or 63 miles due west of Santa Barbara. This event has had a single aftershock so far: a M3.3 at 8:37 am at the same location.

There were also two small quakes, a M2.9 and a M2.6, in northern Mexico, 18 miles southeast of Calexico. There was also a M2.5 at this location yesterday morning, at 9:01 am.

17:08 PST, Thursday, December 10

At 12:02 pm today, there was a M2.7 located in the San Gorgonio Pass area, 2 miles north-northeast of Banning. As far as we know, it was not felt.

We recorded and analysed 124 earthquakes in the past week. Click here to see a summary and map .

09:36 PST, Monday, December 07

On Friday morning at 8:02 am, there was a M2.5 located 3 miles southwest of Redlands, near where the Banning fault intersects the San Jacinto. Then, on Saturday night at 7:20 pm, there was a M2.7 about 5 miles south of Bolsa Chica Beach. This epicenter is near the Newport-Inglewood fault zone. Please remember that, just because small quakes like these are near major mapped faults, does not necessarily mean the major mapped faults are responsible. Quakes in the M2 range can occur of faults that are only a few hundred meters long, and California has a huge number of those. We do not think that either of these two small quakes was felt.

16:56 PST, Thursday, December 03

We recorded and analysed 161 earthquakes in the past week. Click here to see a summary and map .

08:22 PST, Wednesday, December 02

At 1:47 pm on Monday, there was a small Northridge aftershock, M2.5 located 5 miles west of Valencia.

On Tuesday, at 12:47 pm, there was another small quake, also M2.5, located 9 miles northwest of Oceanside. Neither, as far as we know, was felt.

Last updated 17:03 PST December 31, 1998
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