Earthquake Commentary for April, 2000

Map of recent earthquake activity

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17:30 PDT, Thursday, April 27

The week's earthquake list totals 396 this week. Click here to see a summary and map .

09:52 PDT, Wednesday, April 26

Two small quakes were noticed in southern Owens Valley early yesterday evening. They were M2.3 and M3.3, at 6:19 pm and 6:20 pm, respectively. The epicenters were 4 miles northwest of Olancha. This location is at the eastern front of the Sierra Nevada, near the southern end of Owens Lake.

There were also more Obsidian Butte quakes: at 10:37 pm and 10:39 pm, magnitudes M3.3 and M3.5. Epicenters were less than 1 mile southwest of Obsidian Butte. These quakes would be aftershocks of the M3.7 at 11:36 am yesterday. They were probably felt, although we have no reports.

17:56 PDT, Tuesday, April 25

There were a couple of more small quakes this afternoon. A M2.5 occurred at 1:13 pm, 17 miles south-southwest of Palos Verdes Point. At 4:02 pm, there was a M2.9 aftershock of this morning's M4.1 Baja quake, 41 miles south-southeast of Calexico. Neither was reported felt.

12:59 PDT, Tuesday, April 25

Another quake in the upper M3's has occurred: at 11:36 am today, 1 mile southwest of Obsidian Butte (in the northern Imperial Valley), magnitude M3.7. It seems to have been felt, at least in the Niland and El Centro areas.

09:28 PDT, Tuesday, April 25

The largest seismic action overnight actually occurred in northern Baja. This quake had a magnitude of M4.1 and was located 41 miles south-southeast of Calexico (or 47 miles southwest of Yuma AZ). This is definitely an active area, within a few miles of the site of a Mw6.1 quake on June 9, 1980. Although we have no reports, it could easily have been felt in the southern Imperial Valley, and/or in Yuma.

In addition, a M3.1 Hector aftershock went unnoticed at 1:16 am this morning. The epicenter was 36 miles north of Joshua Tree.

There was also a small quake (unfelt?) near Hemet, 8 miles west-southwest of Hemet, to be exact. The time was 10:55 pm last night.

09:08 PDT, Monday, April 24

Further activity this weekend included a M3.4 at 1:48 am on Sunday, located 12 miles north-northwest of Tehachapi. There was also a M3.5 Hector aftershock at 7:42 pm Sunday, located 39 miles north of Joshua Tree. We have had no inquiries about either of these quakes.

13:55 PDT, Saturday, April 22

There was another possibly feelable Hector aftershock early this afternoon: a M3.4 at 12:08 pm. So far, there have been no public calls on it.

10:18 PDT, Saturday, April 22

A M3.2 Hector aftershock occurred early this morning, at 3:25 am. It was located 21 miles north of Joshua Tree.

Other small quakes occurred at 9:07 am, 4 miles north-northeast of Lake Isabella, magnitude M2.7, and at 9:32 am, 6 miles south of Pt. Fermin, San Pedro, magnitude M2.6.

We got no "felt reports" on any of these.

10:53 PDT, Friday, April 21

A couple of small quakes occurred yesterday evening, along the northern front of the San Bernardino Mountains, 8 miles northeast of Big Bear City. The two largest ones were a M2.7 at 7:04 pm and a M3.3 at 8:32 pm. We have no reports that either one was felt.

17:36 PDT, Thursday, April 20

The week's earthquake list totals 313 this week. Click here to see a summary and map .

09:19 PDT, Thursday, April 20

Yesterday afternoon, at 1:25 pm, there was a M2.5 located 7 miles west-northwest of Palomar Observatory. Another M2.5 occurred at 3:13 am today, located 23 miles east of Goldstone Lake in the Mojave Desert. Neither was felt, as far as we know.

A slightly smaller quake, M2.3, occurred at 9:57 pm last night, 4 miles southeast of Diamond Bar. Although this quake was at least in a populated area, we still got no inquiries.

11:24 PDT, Tuesday, April 18

Late yesterday afternoon, a pair of small quakes occurred near Littlerock, 7 miles south-southeast of Palmdale. The first was a M2.6 at 6:22 pm and the other was a M2.5 at 6:26 pm. This location is close to the San Andreas fault, but neither quake has a clear strike-slip focal mechanism, so an fault responsible is probably a subsidiary fault. Neither quake was, as far as we know, felt.

Two more quakes, although smaller, were felt. These occurred 1 mile southwest of Highland Park at 1:18 am (M2.2) and 1:45 am (M1.9). They were felt in Highland Park. Highland Park has had a few very small quakes in the last week, and people seem to be feeling them.

14:02 PDT, Monday, April 17

There was a M3.0 quake at 8:29 am this morning, located 8 miles south-southwest of Morongo Valley (or 11 miles northwest of Palm Springs). We have received no inquiries on it.

The largest quake over the weekend was a M3.9 Hector aftershock, 34 miles south-southwest of Baker. This one occurred at 6:15 pm on Saturday, and was felt in six zip codes, mainly northwest of Barstow.

Other possibly feelable quakes over the weekend included a M2.6 Obsidian Butte quake in the northern Imperial Valley. The epicenter was 3 miles southeast of Obsidian Butte.

There were two noticable Landers aftershocks, a M2.7 at 10:12 pm on Friday, 6 miles north of Yucca Valley, and a M2.9 located 13 miles north of Yucca Valley, at 2:03 pm on Sunday. This latter quake was followed by a M3.1 in the Coso area, 6 miles east-southeast of Coso Junction, at 2:32 pm.

18:36 PDT, Thursday, April 13

The week's earthquake list totals 315 this week. Click here to see a summary and map .

Note that there has been another small quake since the UTC day turned: a M2.6, located 14 miles east-northeast of Olancha. There have been no inquiries.

12:27 PDT, Thursday, April 13

Another small quake, a M2.7 at 11:41 am today, occurred about 14 miles east-southeast of Julian.

09:31 PDT, Thursday, April 13

There was a very small quake possible felt in Mt. Washington yesterday, at 5:50 pm. The magnitude was M1.8. The "felt call" was for about one hour later, but allowing for some confusion, it might have been this quake. The epicenter was about 2 miles north-northwest of Highland Park, but it is very poorly located due some technical problems.

Other quakes overnight include a M2.8 at 8:26 pm, located 5 miles southeast of Coso Junction, and a M2.7 at 12:22 am, located 2 miles south-southwest of Pacoima. We received no inquiries on either of these.

08:40 PDT, Wednesday, April 12

At 1:14 pm yesterday, there was a M2.5 quake 8 miles east of Desert Hot Springs. As far as we know, it was not felt.

Then, at 11:55 pm last night, there was a M2.5 located 6 miles north-northeast of Beaumont. It was not felt either.

08:45 PDT, Tuesday, April 11

The largest quake overnight was a M3.2 at 1:20 am, located 8 miles south-southeast of Olancha. We have no reports of it having been felt.

Later in the morning, at 5:20 am, there was a M2.8 in the Coso Range, 5 miles southeast of Coso Junction. No reports have been received on that one either.

12:05 PDT, Monday, April 10

Here are the Quarterly Statistics! We are still not finished with the backlogged Hector aftershocks, so the "+" means that the figure is a minimum number.

Totals listed below apply to the area within a polygon bounded by
the following latitude, longitude pairs:
35.0N, 121.0W; 37.0N, 119.0W; 37.0N, 115.0W; 32.5N, 115.0W; and
32.5N, 121.0W.

1st quarter 2nd quarter 3rd quarter 4th quarter all 3.0+ all 3.0+ all 3.0+ all 3.0+ 1986 3,040 16 2,865 19 6,634 192 2,300 38 1987 1,679 24 1,887 36 2,341 38 5,748 198 1988 2,749 40 2,128 45 2,195 30 2,208 27 1989 2,528 46 2,340 21 2,323 19 2,335 26 1990 2,850 56 2,293 43 1,859 27 2,039 31 1991 1,679 10 1,843 32 2,081 21 2,337 27 1992 3,389 37 10,084 741 25,849 808 9,775 181 1993 4,799 41 5,152 58 5,039 46 4,419 34 1994 10,735 418 5,766 42 5,221 48 4,813 39 1995 3,639 28 3,788 37 8,252 88 7,733 49 1996 5,735 56 3,966 32 3,690 23 4,660 50 1997 3,699 39 3,276 54 3,193 31 2,443 27 1998 3,590 56 2,830 27 2,655 37 2,352 29 1999 2,253 35 2,546 58 2,555 36 8,306+ 468+ 2000 5,295 72 --------------------------------------------------------------------

11:06 PDT, Monday, April 10

At 11:52 pm on Saturday night, a quake was felt in Fontana. Magnitude was M3.6 and the epicenter was 3 miles northwest of Fontana. It had a few small aftershocks, the largest of which was a M2.8 this morning at 10:03 am.

There was also action in the southern Imperial Valley, 6 miles east-northeast of Calexico. Magnitude was M4.3. The location is not far from the Imperial fault, and the focal mechanism agrees. This quake was felt thoughout the southern Imperial Valley.

In addition, there were a few Hector aftershocks, including a M3.0 at 11:18 am on Saturday and a M3.6 at 6:33 pm last night, both located about 35 miles south-southwest of Baker.

Last night at 10:26 pm, there was a small quake (M2.6), located 3 miles northeast of Camarillo. As far as we know, no-one noticed. At 4:31 am this morning, there was another unrelated M2.6 located 16 miles south-southwest of Ocotillo Wells (which is near Borrego Springs).

17:23 PDT, Thursday, April 06

The week's earthquake list totals 377 this week. Click here to see a summary and map .

08:50 PDT, Thursday, April 06

We had another M3+ Hector aftershock yesterday, at 1:38 pm. The magnitude was M3.3, and the epicenter was located 25 miles north of Joshua Tree.

09:15 PDT, Tuesday, April 04

There was a M3.6 Landers aftershock at 11:59 am yesterday. The epicenter was located 8 miles south of Joshua Tree. It does not appear to have been felt by anyone.

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Last updated 17:30 PDT April 27, 2000.