Log in to view full website content, join discussions, and to post information.

Recent comments

  • oskin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    The lineament visible on the radar east of the main rupture lies directly on the mapped trace of the airport strand of the west Napa fault. As far as I know this rupture has not been mapped in the field. I am not familiar with the COSMO-Skymed instrument. Looks like a little more than 1/2 fringe of displacement. Assuming pure RL slip, how much may there be? 

  • shyun
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    Good morning. I posted a kmz and a snapshot of COSMO-SkyMed coseismic interferogram at the following URLs. The zoomable wrapped interferogram can help locating surface ruptures. For example, there seems to be one about 2.5 km east from the epicenter, running parallel to what Mike Oskin mapped.

    http://aria-share.jpl.nasa.gov/events/20140824-napa/ARIA_NapaEQ_CSK_D74_...

    http://aria-share.jpl.nasa.gov/events/20140824-napa/ARIA_NapaEQ_CSK_D74_...

    -- Sang-Ho Yun, JPL-Caltech ARIA project

  • dreger
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    Thanks Alex

  • walls
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    5Hz GPS data for stations within 300km is available for 2014-08-24 (full day) at: ftp://data-out.unavco.org/pub/highrate/5-Hz/rinex/2014/236/

    1Hz 8/21 - 8/27 UTC (7 full days) is in the process of being downloaded.


    UNAVCO South Napa Earthquake Event Page: http://www.unavco.org/highlights/2014/south-napa.html
     

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Marjorie Greene (EERI) 8/26/14 17:57PDT:

    Just FYI--
    There will be a third briefing tonight. Then we will close the physical clearinghouse, although we know of a few more teams that will still be coming tomorrow--We will encourage people to contribute data and observations via the virtual clearinghouse.

    ___________________________________________________

    Our evening Clearinghouse briefing will take place at 6:00 p.m. Tuesday, August 26th at 3161 Jefferson Street in Napa.

    If you are not able to participate in person, we have set up a webex. The call in number for audio for the webex is the same as the call in number for the briefing

    callin briefing and audio for webex:
    866-828-5695
    passcode: 8077172

    -------------------------------------------------------
    Meeting information
    -------------------------------------------------------
    Topic: Clearinghouse Evening Briefing
    Date: Tuesday, August 26, 2014
    Time: 6:00 pm, Pacific Daylight Time (San Francisco, GMT-07:00)
    Meeting Number: 745 107 585
    Meeting Password: (This meeting does not require a password.)

    -------------------------------------------------------
    To start or join the online meeting
    -------------------------------------------------------
    Go to https://resources.webex.com/resources/j.php?ED=277401287&UID=497322317&R...

    -------------------------------------------------------
    Teleconference information
    -------------------------------------------------------
    call-in 866-828-5695
    password: 8077172

    -------------------------------------------------------
    For assistance
    -------------------------------------------------------
    1. Go to https://resources.webex.com/resources/mc
    2. On the left navigation bar, click "Support".
    To add this meeting to your calendar program (for example Microsoft Outlook), click this link:
    https://resources.webex.com/resources/j.php?MTID=m80dd10c791820180d53eb9...

    To check whether you have the appropriate players installed for UCF (Universal Communications Format) rich media files, go to https://resources.webex.com/resources/systemdiagnosis.php.

    http://www.webex.com

    Thanks

  • jhardebeck
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    Here's a text file with the locations.

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    near northern aftershock cluster.

    From Mike Oskin (UC Davis) 8/26/14 17:05 PDT:

    I received an email report of some possible surface rupture along Dry Creek road, about 3.5 km NW of Alston Park. This is well outside the zone of surface ruptures mapped thus far (that I am aware of). Could just be landsliding. However it is along the trace of the west Napa fault mapped by Wesling and Hanson, and its immediately updip of the cluster of aftershocks in this area. So I think that somebody should check this out when they get the chance. Email pasted in below. KMZ and google earth map attached.

    -Mike Oskin

    Hi Mike
    I've been following your twitter feed after the S.Napa quake, and I perhaps have some extra info for you.
    At 4155 Dry Creek Road, at my in-laws house, there is a large new crack that has appeared on the driveway, very approx 4m long and maybe 5cm wide at its widest point. I notice also that the neighbor to the immediate South on the road also has a long crack and mild "tenting" that has appeared across his driveway. I don't know how the faults run at this point.

    coordinates are approx: 38.3484591,-122.3573352

    Hopefully this can be of use in your research- I note that a lot of aftershocks were centered just behind this property but my knowledge doesn't permit me to know if that is relevant or not!


    regards

    Nick Guest

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    A short press release on aftershocks and revised probabilities:

    http://www.usgs.gov/newsroom/article.asp?ID=3981#.U_0hwkiRaRJ

  • aemorelan
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

     Doug,

    I have linked to a csv file with a list of our measurements that I have the most confidence in. The first ten rows are measurements along the main fault trace. The remaining four lie along the trace across the 500 meter jump to the east. All measurements are right lateral and in centimeters.

    https://ucdavis.box.com/s/a4ca3vfyt66cyxrvhu6l

    -Alex

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Jeanne Hardebeck (USGS) 8/26/14 15:29 PDT:

    Hi everyone,

    I've attached a revised set of earthquake relocations, based on our 3D seismic velocity model with relative locations refined using hypoDD. The main aftershock cluster in the mainshock hypocentral area (cross-section C-D) roughly defines a steeply SW-dipping structure. The recent aftershocks to the south of the mainshock are generally consistent with this apparent structure.

    The two northern clusters of seismicity (cross-section A-B) suggest a possible structure with a ~50° dip to the SW. I have been unable to obtain any good focal mechanisms for the events in these clusters to verify a dipping fault plane.

    I will post the updated relocation text files to the google drive site.

    Cheers,
    Jeanne

  • owen
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    Am sending revised plot & table of offsets that cover a larger area around the earthquake.

    The offset table uses same data as earlier posted table - 7 days of daily positions from before the earthquake and a static position from ~13.5 hours after the earthquake (RED vectors in each plot)

    The "compare" plot shows results of differencing pre-earthquake position from daily solution from Sunday August 24 @ 5 pm - Monday August 25 @ 5 pm (UTC day 237). It indicates that there's no significant postseismic slip at this time and that increase in surface rupture reported from Sunday to Monday is likely due to slip occurring at very shallow depths. 

    Thanks,

    Sue, Angie, Zhen 

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Tom Brocher (USGS) 8/26/14 13:07 PDT:
     

    The PGA recorded for Sunday's mainshock on one of the NetQuakes instruments, N016, from downtown Napa (on Main St. close to 1st St.), is 63% g on the north component. We have verified this estimate by manually checking the recorded waveform (attached). This record is from an area having a large number of red tags.

    The data for this instrument had to retrieved manually yesterday (due to a poor wireless connection). Jim Luetgert, NetQuakes manager, said that there may be a small (20 msec) timing error in the record that he is looking into. This timing error is not important for ShakeMap or posting at the CESMD.

    We are currently working to fix the timing and to post this record on the CESMD website.

    Please share this observation with the EERI and GEAR field team.

    Anne Rosinski and Luke Blair: Please be sure to report this to the Clearinghouse.

    Tom

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Tom Brocher (USGS) 8/26 14:02 PDT:

    I'm attaching a couple of screen shots that juxtapose the red tagged buildings in Downtown Napa with Wentworth and Knudsen's liquefaction hazard map for the Bay Area (OFR 00-444). Many of the red tags are along the Holocene alluvial deposits along the Napa River and Napa Creek (red and orange hazard units). The green unit represents undifferentiated Quaternary fan deposits.

    Tom

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Keith Knudsen (USGS) 8/26/14 13:57 PDT:

    These Quaternary map data are from Witter et al 2006; USGS OFR 2006-1037

    To download GIS data see http://pubs.usgs.gov/of/2006/1037/Feel free to consult with me regarding interpretation of the mapping and map units.  Keith
  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    Forwarded by Tom Brocher (USGS) 8/26/14 13:33 PDT:

    I'm forwarding maps of Quaternary and Holocene deposits in Napa that suggest that the strong shaking correlates to mapped units of Holocene/Historic alluvial deposits (Qhay) along the Napa River and Napa Creek in Downtown Napa.

    We'll get these maps into kml so we can compare the to location of red tagged buildings.

    Tom

    ---------- Forwarded message ----------
    From: Wentworth, Carl (USGS)
    Date: Tue, Aug 26, 2014 at 2:12 PM


    Keith:

    Just to remind you that the Quaternary map (OFR 2000-444) may be of interest in looking at the distribution of damage in Napa. See attached images, one from the map graphic, the other (largely black) of the lines and labels in the GIS file (included for easy identification of the units). The town/city of Napa is marked with an N and leader on the colored map - it's located mostly west of the N-S river (Napa R.). Areas of water (blue) and of unit Qhay (orange) are colored on the GIS image.

    FYI - In her San Jose State Univ. Ms thesis, Nan Shostak found that 1906 damage in the Santa Clara Valley seemed to correlate with the thickness of the post-glacial alluvial unit as I determined it from wells (my cycle 1).

    Cheers,

    Carl

  • donnellan
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    We are working on obtaining UAVSAR flights as soon as possible. The earthquake occurred in the area led by Andrea Donnellan and Jay Parker, but also impacts flight lines by Eric Fielding, Roland Burgmann, and Cathleen Jones. We inverted the ARIA GPS solution for a single right-lateral vertical fault with the following results:

    Lon                   -122.29 ± 0.04° (lower left (SE) corner)
    Lat                       38.20 ± 0.03°
    strike                  -22.78 ± 5.73°
    dip                              90 Fixed
    depth                     7.10 ± 3.82 km
    width                     5.53 ± 3.45 km
    length                  15.07 ± 8.50 km
    strike-slip        -594.68 ± 24.77 mm
    dip-slip                        0 mm Fixed
    Geodetic Moment: 1.50E+25 dyne cm^2
    Geodetic Magnitude: 6.1
     

    Attached are interferograms from this model for flight lines heading 055° and 235°.

  • herring
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

     Attached is a PDF file with coseismic offsets (50% confidence error ellipses) from the continous GPS sites in the region.  The tabluar values are (based on splitting the data from 8/24/2014 into sections between 0:00-10:21 GPST and 10:24-24:00 GPST).  Text file attached as well.

    * Coseismic displacements from napa_01.org for earthquake 34 :  Date Tue Au6:43 EDT 2014

    * Offset based on difference between 10:24-24:00 GPST 8/24 and 0:00-10:21 GPST 8/24.

    *  Long      Lat       dE       dN         E +-     N +-    dH       H +-  Site

    *   deg      deg       mm       mm         mm       mm      mm       mm 

     237.62324  37.91455     1.35     2.86       2.47     3.11   -1.24     6.35 P181 

     237.18374  38.18572    -0.92     0.20       2.33     2.81   -0.47     4.38 P194 

     237.25736  38.29814    -2.88     1.88       2.28     2.84   -0.51     5.32 P196 

     237.23261  38.42856    -3.48     0.88       2.14     2.60    0.77     4.08 P197 

     237.39255  38.25988    -7.78     4.21       2.61     3.36    0.24     8.72 P198 

     237.49656  38.26369   -19.47     8.62       2.76     3.59    2.74    11.31 P199 

     237.54830  38.23983   -16.12    13.78       3.19     4.20    1.79    13.81 P200 

     237.50400  38.42358   -13.00     6.82       2.46     3.02    0.27     7.98 P202 

     237.78094  37.86390    -0.25     1.33       1.71     2.16   -1.00     4.60 P224 

     237.78246  38.15296    29.17   -16.27       7.11     4.47   -4.09    14.81 P261 

     237.57082  38.57769    -1.41    -1.76       2.31     2.80   -0.30     4.89 P263 

     237.80467  38.44421    -7.49   -17.50       2.67     3.45   -1.37     8.58 P264 

     238.15647  38.18397     2.63    -2.23       2.46     3.02   -0.37     4.93 P266 

     238.17676  38.38034     0.98    -0.32       2.31     2.71    0.28     4.07 P267 

     237.47368  38.03318     2.60     4.77       2.43     3.09    2.05     7.94 SVIN 

     238.05306  38.39453    -0.38    -0.86       2.26     2.81    1.28     5.53 VCVL 

     
  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Justin Pressfield (USGS) 8/26/14 11:33 PDT:

    https://www.youtube.com/watch?v=LQhYbfIz0n4

    Not condoning the use of a quad-copter/drone. But you all may find this useful.

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    Response by Erol Kalkan (USGS) to Jack Boatwright regarding downtown Napa buildings of engineering interest for deploying instruments 8/26/14 10:36am:

    Jack,

    1. US Post Office (masonry structure) got damaged and red-tagged (see photo). The lot of this building would be a good location for deploying an instrument.
    2. Napa River bank in downtown is unstable and locals say the cracks on nearby roads are opening - this would be another location for monitoring (see photo).
    3. I also observed damage away from downtown (Old Sonoma Rd.), the buildings in mental health facility got some damage (see photo), this may be another location to consider.
    4. The neighborhood of St. John Baptist church/school got quite damage. In fact, the church is red-tag and school has some minor damage visible from outside. One instrument can be located at the school parking lot. There is historical Pfeiffer building built around 1875 completely damaged nearby (see photos).
    5. One more instrument along 2nd or 3rd street in downtown will be great.
     

    When locating instrument, instead of NS-EW direction orientation, it would be better to locate them so the instrument axes will align with the grid of downtown.

    Please let me know if you need more locations.

    Erol

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Bill Barnhart (USGS) 8/26 11:06am:

    Updated geodetic report for South Napa with today's GPS updates from Menlo Park.

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Rob Graves (USGS) 8/26 10:39am:

    All-

    The feature that Erol noted where the damage in Napa suggests a strong SW-NE polarization of ground motion
    is qualitatively consistent with rupture directivity to the NW on a predominantly SS rupture, as indicated in the
    slip model derived by Dreger et al. I haven't had the chance to look at any of the ground motion records, but it would
    be interesting to see if this idea can be further quantified with the recordings.

    -Rob

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Erol Kalkan (USGS) 8/26/14 10:28 PDT:

    I was in Napa yesterday, and took more than 250 photos. I walked through each block in downtown area where most of the damaged buildings are. I also visited nearby locations around Napa based on reports from local people. Overall, downtown Napa is affected worse by this earthquake.

    The most interesting observation from the damaged buildings is that the ground motion was polarized in one direction where the downtown buildings are oriented. Buildings shook more violently in this direction than the perpendicular direction. Block by block, the damage in buildings was concentrated only on NE-SW direction.

    Masonry buildings were the ones that suffered the most significant damage as expected. Buildings designed according to the modern building codes are intact. Some of the modern buildings suffered damage as hair-cracks on their facade. One modern building got damage due to differential settlement associated with underlying soft soil.

    Surprisingly, soft-story mechanism didn’t occur.

    There were number of broken water lines as well as cracking on roads due to settlement and possible liquefaction. Liquefaction was also occurred on Marina district.


    Attached are few photos to highlight the extent of damage in the downtown area.


    I am going to upload all photos to share-drive, then a short engineering report explaining the damage conditions in Napa will follow. Please let me know if you have any questions.

    Erol
     

  • whammond
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    Sue, Angie & Zhen Liu --

    Just became aware of this blog.  We also estimated coseismic offsets from Geoff Blewitt's 24 hour latency/5 minute sample rate solutions.  Results look similar to yours:

    http://geodesy.unr.edu/billhammond/earthquakes/nc72282711/nc72282711.html

    We used 6 hours of data before and 6 hours after the event with a one hour gap after the event.  The link includes some plots of time series, links to others and a text file with offset estimates.  Offsets consistent with a strike slip event with epicenter near the West Napa fault zone.

    -Bill

     

     

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

    From Luke Blair (USGS) 8/26/14 09:21 PDT.

  • ingrid
    2014.08.24 - M6.0 South Napa Earthquake, California   7 years 49 weeks ago

     Hello all,

      5hz GPS data for the hour of the earthquake has been posted to the NCEDC at http://www.ncedc.org/ftp/pub/gps/5-hz/rinex/2014/2014.236/   Right now, this is just BSL-operated sites, but we will add other stations that regularly archive at the NCEDC if and when they become available.

      1hz data for the entire day is available from the NCEDC at http://www.ncedc.org/ftp/pub/gps/highrate/rinex/2014/2014.236/

    If you do use this data, please drop me a note at ingrid@seismo.berkeley.edu; I would be curious to know how widely its used.  Thanks,

         -Ingrid