Rupture Directions for Selected Northern California Earthquakes

Fault rupture tends to focus wave energy along the fault, a phenomena called directivity. The table below links to results from a simple inversion of peak ground motions to estimate rupture direction and rupture velocity. We correct the horizontal peak accelerations (PGA) and peak ground velocities (PGV) from Northern California ShakeMap data for site amplification and source-receiver distance to obtain a set of residual peak S-wave motions. We fit these residual peak motions using the directivity function for a unilateral line source (see detailed explanation). The rupture direction is not constrained to lie along a nodal plane: good solutions yield rupture directions close to a nodal plane. Events with slow rupture velocities are ambiguous: they could be either complex or bilateral ruptures, or slow unilateral ruptures. We have created seismicity maps and cross sections for earthquakes with M ≥ 4.0 and more than 7 aftershocks.

Our results for earthquakes occurring from 1998 to 2008 are presented in Seekins and Boatwright, 2010, Rupture Directivity of Moderate Earthquakes in Northern California, Bull. Seismol. Soc. Am. vol 100, pp 1107-1119.

Questions and comments about this page should be addressed to Jack Boatwright.

MagLocationDateTimePlotsLatLonDepthEvent ID
6.8Eureka03/09/201422:18 PDTDirectivityN40.83W125.1316.6 km72182046
4.5The Geysers01/12/201412:24 PSTDirectivityN38.81W122.822.6 km72141176
4.0Petrolia01/01/201422:23 PSTDirectivityN40.29W124.4520.3 km72134626
4.1Ferndale12/17/201305:28 PSTDirectivityN40.69W124.5117.8 km72125816
4.1Lost Hills12/12/201323:49 PSTDirectivityN35.81W119.822.2 km72119970
3.6Angwin12/05/201322:44 PSTDirectivityN38.68W122.3910.3 km72115885
3.7Gilroy12/02/201302:05 PSTDirectivityN36.94W121.546.8 km72113080
3.4Hayfork11/20/201316:48 PSTDirectivityN40.37W123.7229.5 km72110711
3.3Danville11/13/201309:30 PSTDirectivityN37.79W121.9710.3 km72106876
4.9Bayview10/11/201316:05 PDTDirectivityN40.98W124.758.7 km72086051
3.9Rio Dell10/04/201307:42 PDTDirectivityN40.44W124.1526.3 km72080926
3.6Canyondam08/19/201304:09 PDTDirectivityN40.16W121.031.4 km72052151
4.5Bayview08/02/201319:25 PDTDirectivityN40.81W124.420.5 km72042291
3.9San Juan Bautista06/27/201320:52 PDTDirectivityN36.76W121.476.9 km72016695
3.6Canyondam05/30/201314:08 PDTDirectivityN40.18W121.14.8 km72003545
5.7Canyondam05/23/201320:47 PDTDirectivityN40.19W121.069.7 km71996906
3.5San Jose05/09/201322:12 PDTDirectivityN37.37W121.736.6 km71988946
3.9Petrolia05/01/201314:03 PDTDirectivityN40.3W124.388.8 km71980360
4.5The Geysers03/14/201302:09 PDTDirectivityN38.81W122.792.2 km71954065
3.9Pinnacles10/28/201221:25 PDTDirectivityN36.59W121.29.0 km71870540
3.5Willow Creek10/21/201213:40 PDTDirectivityN40.9W123.9321.7 km71864295
3.6King City10/21/201200:37 PDTDirectivityN36.31W120.859.5 km71863730
5.3King City10/20/201223:55 PDTDirectivityN36.31W120.869.4 km71863625
4.5Ukiah09/25/201208:15 PDTDirectivityN39.17W123.179.9 km71847715
4.0Rio Dell09/14/201211:19 PDTDirectivityN40.44W124.1626.8 km71842255
4.4Rio Dell09/14/201204:53 PDTDirectivityN40.44W124.1927.2 km71842075
4.1Avenal09/07/201206:23 PDTDirectivityN36.12W12010.5 km71839170
3.3Parkfield08/31/201214:44 PDTDirectivityN35.99W120.564.4 km71835625
3.3New Idria07/19/201200:59 PDTDirectivityN36.49W120.7410.8 km71818621
4.0Willow Creek07/12/201203:39 PDTDirectivityN40.75W123.6830.4 km71815561
4.4Fort Bragg07/08/201205:05 PDTDirectivityN39.48W123.88.1 km71812891
3.5Willits06/25/201206:24 PDTDirectivityN39.46W123.325.5 km71806361
3.5Morgan Hill06/03/201210:31 PDTDirectivityN37.26W121.647.2 km71795731
3.9The Geysers05/13/201205:38 PDTDirectivityN38.79W122.783.5 km71784801
4.5The Geysers05/05/201202:23 PDTDirectivityN38.8W122.762.8 km71776130
4.1Bayview04/17/201213:31 PDTDirectivityN40.97W124.4219.8 km71766345
3.5Aromas04/13/201215:18 PDTDirectivityN36.89W121.636.6 km71764230
3.7Pinnacles04/05/201220:16 PDTDirectivityN36.56W121.125.6 km71759475
4.0Richmond03/05/201205:33 PSTDirectivityN37.93W122.39.2 km71746766
3.4Pinnacles03/01/201209:15 PSTDirectivityN36.64W121.256.5 km71744566
3.7Weitchpec02/28/201221:00 PSTDirectivityN41.14W123.830.6 km71743876
4.3Petrolia02/24/201221:17 PSTDirectivityN40.29W124.3220.0 km71741671
3.5Vallejo02/16/201209:13 PSTDirectivityN38.08W122.238.3 km71736656
3.5Vallejo02/15/201218:09 PSTDirectivityN38.08W122.238.8 km71736351
5.6Weitchpec02/13/201213:07 PSTDirectivityN41.14W123.7928.2 km71734741
4.3The Geysers02/12/201220:47 PSTDirectivityN38.79W122.750.4 km71729135
3.6Berkeley10/27/201105:36 PDTDirectivityN37.87W122.268.2 km71671256
4.7Whitehawk10/26/201123:37 PDTDirectivityN39.61W120.4713.9 km71671056
3.8Berkeley10/20/201120:16 PDTDirectivityN37.86W122.268.0 km71667591
4.0Berkeley10/20/201114:41 PDTDirectivity, AftershocksN37.86W122.258.1 km71667366
3.2San Leandro09/25/201120:08 PDTDirectivityN37.75W122.157.9 km71653461
3.6Pinnacles08/27/201100:21 PDTDirectivityN36.6W121.26.9 km71627850
4.6Pinnacles08/27/201100:18 PDTDirectivity, AftershocksN36.58W121.187.8 km71627835
3.4San Leandro08/24/201109:57 PDTDirectivityN37.75W122.158.7 km71625585
4.2Mammoth Lakes08/24/201104:59 PDTDirectivityN37.55W118.8710.0 km71625245
3.6San Leandro08/23/201123:36 PDTDirectivityN37.74W122.158.1 km71625060
3.7Anderson Springs08/17/201102:02 PDTDirectivityN38.79W122.753.0 km71621065
3.8Tres Pinos07/06/201100:18 PDTDirectivityN36.67W121.297.6 km71596420
3.4Hercules05/21/201119:04 PDTDirectivityN37.98W122.259.8 km71573330
3.4San Bruno04/18/201114:57 PDTDirectivityN37.6W122.4512.5 km71560691
3.9Lopez Point04/05/201104:56 PDTDirectivityN36.07W121.6210.7 km71547875
4.5The Geysers02/28/201118:19 PSTDirectivityN38.82W122.823.0 km71530230
3.9San Juan Bautista01/12/201120:00 PSTDirectivityN36.8W121.547.3 km71509345
4.5San Juan Bautista01/12/201100:51 PSTDirectivity, AftershocksN36.77W121.58.0 km71508850
4.1Seven Trees01/07/201116:10 PDTDirectivityN37.29W121.6610.4 km71506865
3.9Aromas08/09/201017:51 PDTDirectivityN36.91W121.645.4 km71444201
3.6Tom's Place08/05/201018:20 PDTDirectivityN37.62W118.817.8 km71442046
3.8Tom's Place07/22/201004:40 PDTDirectivityN37.62W118.818.3 km71434941
4.0The Geysers07/15/201008:31 PDTDirectivityN38.82W122.812.7 km71425345
3.8Hayfork07/10/201009:04 PDTDirectivityN40.43W123.5731.9 km71422700
3.7The Geysers06/14/201003:39 PDTDirectivityN38.80W122.784.3 km71415021
3.6Aromas06/11/201023:05 PDTDirectivityN36.86W121.617.7 km71413856
3.6The Geysers03/28/201002:39 PDTDirectivityN38.81W122.822.6 km71369580
3.5Tres Pinos02/08/201011:56 PDTDirectivityN36.72W121.363.2 km71350686
3.7The Geysers01/30/201001:32 PSTDirectivityN38.83W122.802.8 km71346081
3.7Milpitas01/08/201011:48 PSTDirectivityN37.48W121.7910.2 km71337451
4.1Milpitas01/07/201010:09 PSTDirectivityN37.48W121.789.0 km71336726
4.1Redway01/04/201006:24 PSTDirectivityN40.28W123.8730.7 km71330090
3.8The Geysers12/20/200904:26 PSTDirectivityN38.79W122.774.4 km71324305
3.7The Geysers11/24/200903:59 PSTDirectivityN38.82W122.792.7 km71318526
3.5Pinnacles11/01/200906:55 PSTDirectivityN36.63W121.2511.0 km71303390
3.6The Geysers10/30/200923:52 PDTDirectivityN38.79W122.774.8 km71302365
3.7Sunol10/13/200920:27 PSTDirectivityN37.63W121.888.171299286
3.6Aromas09/09/200911:45 PDTDirectivityN36.90W121.635.0 km71278336
3.9Hollister09/06/200902:47 PDTDirectivityN36.85W121.419.5 km71271995
3.8Templeton09/05/200920:20 PDTDirectivityN36.56W120.85.3 km71271840
3.7The Geysers07/06/200922:03 PDTDirectivityN38.84W122.802.9 km71244841
3.8The Geysers06/30/200910:27 PDTDirectivityN38.81W122.794.0 km71241391
4.4Lake Nacimiento06/20/200905:32 PDTDirectivityN35.64W120.956.1 km40238431
3.7Danville06/08/200915:15 PDTDirectivityN37.82W121.968.1 km40237825
4.2Pine Hill05/03/200910:54 PDTDirectivityN40.25W124.1621.0 km51220943
3.7The Geysers04/17/200908:09 PDTDirectivityN38.82W122.82.7 km51220062
4.3Morgan Hill03/30/200910:40 PDTDirectivityN37.28W121.627.7 km40234037
3.7The Geysers02/20/200902:29 PSTDirectivityN38.81W122.812.3 km40231987
3.7Tres Pinos02/05/200916:20 PSTDirectivityN39.69W121.324.8 km40231391
4.2The Geysers01/04/200909:27 PSTDirectivityN38.78W122.774.3 km51214595
4.1Tres Pinos12/21/200809:35 PSTDirectivityN36.68W121.306.9 km51213534
3.5Templeton11/15/200809:50 PSTDirectivityN35.52W120.804.0 km51211277
4.0Alamo09/05/200821:00 PDTDirectivityN37.87W122.0016.2 km51207740
3.7Paso Robles07/06/200801:25 PDTDirectivityN35.64W120.766.5 km40220309
3.5Alamo06/06/200802:02 PDTDirectivity, AftershocksN37.82W122.077.7 km51203888
3.9American Canyon06/03/200819:29 PDTDirectivityN38.24W122.1810.8 km51203773
5.4Willow Creek04/29/200820:03 PDTDirectivity, AftershocksN40.84W123.529.1 km40216664
3.9Templeton04/29/200810:45 PDTDirectivityN35.5W120.782.7 km40216634
3.7Bayview04/21/200803:00 PDTDirectivityN40.78W124.2121.1 km40215734
3.9The Geysers12/01/200712:50 PSTDirectivityN38.81W122.792.4 km40206647
4.1Ferndale11/08/200719:37 PSTDirectivityN40.54W124.423.6 km40205250
5.4Alum Rock10/30/200720:04 PDTDirectivity, AftershocksN37.43W121.789.2 km40204628
4.1Coalinga09/12/200705:41 PDTDirectivityN36.24W120.3111.6 km40201735
4.2Piedmont07/20/20074:42 PDTDirectivity, AftershocksN37.81W122.115.8 km40199209
4.3San Juan Bautista07/02/200712:58 PDTDirectivity, AftershocksN36.88W121.628.5 km51183708
4.6Mammoth Lakes06/12/200722:23 PDTDirectivityN37.54W118.8814.2 km51182810
4.5The Geysers04/24/200714:08 PDTDirectivityN38.8W122.791.7 km51181154
4.2Lafayette03/01/200720:40 PSTDirectivity, AftershocksN37.9W122.116.6 km40194055
3.8Glen Ellen01/12/200703:27 PSTDirectivityN38.39W122.619.7 km51177644
3.5Berkeley12/23/200609:21 PSTDirectivityN37.86W122.249.8 km51177121
3.7Berkeley12/22/200622:49 PSTDirectivityN37.86W122.2410.0 km51177103
3.7Berkeley12/20/200612:28 PSTDirectivityN38.86W122.249.0 km51177042
4.0Hollister11/29/200613:20 PSTDirectivityN36.85W121.453.0 km40191319
4.4Glen Ellen08/02/200620:08 PDTDirectivity, AftershocksN38.36W122.599.1 km40187964
3.7Alamo03/21/200613:41 PSTDirectivityN37.81W122.0713.2 km51169283
4.4East of San Jose02/05/200510:43 PSTDirectivity, AftershocksN37.39W121.497.0 km51156428
4.3Willow Creek12/4/200417:48:04 PST DirectivityN40.74W123.8021.0 km40169129
4.0Templeton10/02/200405:22 PDTDirectivityN35.54W120.819.2 km51149570
3.6Livermore04/29/200412:49 PSTDirectivityN37.73W121.8219. km40156432
3.6Morgan Hill01/30/200418:11 PSTDirectivityN37.1W121.577.2 km40152518
3.5Livermore01/20/200422:23 PSTDirectivityN37.72W121.8218.8 km51136961
3.7Morgan Hill11/06/200314:04 PSTDirectivityN37.21W121.667.4 km51132794
3.5Orinda10/19/200308:32 PDTDirectivityN37.91W122.159.8 km51132363
3.9Berkeley09/04/200318:39 PDTDirectivityN37.85W122.2212.4 km40146204
3.8San Jose05/26/200303:01 PDTDirectivityN37.31W121.688.6 km51128417
4.3Santa Rosa05/25/200312:09 PDTDirectivityN38.46W122.706.7 km51128377
4.0San Ramon02/02/200310:47 PSTDirectivityN37.75W121.9416.651125530
4.2San Ramon02/02/200310:22 PSTDirectivityN37.74W121.9416.5 km51125525
3.6San Ramon02/02/200308:22 PSTDirectivityN37.75W121.9416.6 km51125511
4.3Hollister01/07/200314:29 PSTDirectivityN36.81W121.398.5 km40139808
3.6Pacifica12/24/200212:22 PSTDirectivityN37.60W122.489.7 km40139437
4.9Gilroy05/13/200222:00 PDTDirectivity, AftershocksN36.97W121.607.0 km40133364
3.7Rio Vista05/08/200207:59 PDTDirectivityN38.23W121.8419.2 km40133251
3.7Rohnert Park07/06/200108:07 PDTDirectivityN38.34W122.637.1 km40124461
4.4San Jose02/25/200115:18 PSTDirectivity, AftershocksN37.33W121.707.8 km51105698
3.5Alameda02/02/200119:41 PSTDirectivityN37.79W122.1712.8 km51105129
5.1Yountville09/03/200001:36 PDTDirectivity, AftershocksN38.38W122.419.4 km51101203
3.6Concord07/15/200004:56 PDTDirectivityN37.97W122.0414.8 km51099915
4.7Bolinas08/17/199918:06 PDTDirectivity, AftershocksN37.91W122.697.9 km40104152
5.1San Juan Bautista08/12/199807:10 PDTDirectivity, AftershocksN36.75W121.469.1 km30190473