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  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 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   3 years 7 weeks ago

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

  • ingrid
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 7 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

  • mfloyd
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 7 weeks ago

    As Gareth has previously informed the community, he and I (with equipment and field assistants from UC Riverside and Berkeley) set up 11 GPS receivers at previously observed survey marks around the epicentral region within about 15 hours of the event.

    Yesterday, I added two more sites (MADR and M139) and, given the mapped rupture, we removed some sites (X552 and 6908) to place them further north (B468 and VETH).

    See attached KML and screen shot of current UCR-MIT survey GPS. The USGS has been working in parallel with us to reoccupy sites that they have previous observations from (see http://earthquake.usgs.gov/monitoring/gps/NCalifornia_SGPS/ or http://earthquake.usgs.gov/monitoring/gps/data/networks/USGS_campaign_da...).

    Cheers,
    Mike

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 7 weeks ago

    From Steve DeLong (USGS) 6/26/14 06:05 PDT:

    Hi Dan, Interesting. Has anyone checked the attached location, it may be a bit farther south and across Buhman from what you describe? Photo and kmz attached. Observed from helicopter. If verified, it would change the trace mapped through to Henry Rd a bit, shifting it eastward. This photo is from shared photos on google drive DeLongOverflightPhotosAug24. DSC_0583

    Best,

    Steve

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 7 weeks ago

    From Dan Ponti (USGS) 8/26/14 01:36 PDT:

    All -

    Tom Holzer, Tim Dawson and I observed well-expressed right-lateral and transpressive faulting in natural ground just west of Buhman Ave between Twin Oaks Drive and Congress Valley Rd. Right lateral displacement within the ~0.4 km long zone that we were able to access is the largest observed to date, and is on the order of 40 cm, with the maximum displacement measured at 46 cm. Over the region we examined, strike of the fault rupture changed from ~345 deg. northward to nearly 0 deg. As the strike changes to the northerly trend, displacement sense changes from nearly pure strike-slip to a more transpressive rupture with notable vertical offset on the order of 15-20 cm (down to the east) and E-W shortening estimated at 10-15 cm. This observation would indicate a clockwise rotation in the slip vector to a N-NE orientation in association with the change in fault strike.

    Although we were unable to walk out the zone today farther to the north and south due to time and access constraints, the zone of fault rupture projects to the north to where UC Davis investigators reported offsets at Oak Rock and Leaning Oak Drives, and to the White Cliff Circle area where the deformation zone trends N-NE and several investigators have reported dominantly compressive deformation, evidenced by pavement buckling and tented sidewalks. To the south these large ruptures likely connect with cracking and small displacements noted at Henry Road near the intersection of Buhman Ave. In the vineyards to the south of the zone we mapped, the fault zone appears to become broader, and more diffuse although this needs to be verified with additional mapping. Some afterslip may be occurring, based on anecdotal comments from residents who described several cracks as growing in width on the order of 1 inch since the earthquake. Based on these same accounts, however, we would infer that most of the observed displacement is coseismic.

    The region of large displacement occurs approximately 8.4 km NW of the epicenter of the mainshock, which is in the region where the preliminary finite fault model from UC Berkeley shows high slip within a few km of the surface. It also appears to be coincident with a bedrock fault shown by Graymer that juxtaposes Cretaceous and Paleogene sediment.

    I've attached an image showing the location of rupture zone we documented in red, along with a couple of photographs to give you the flavor of the rupture character. Tom and I have a lot more photos and measurements that we will upload onto the Google Drive Tuesday.

    Dan

  • huynht
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 7 weeks ago

    Emailed by Ian Dixon (SAS Chief, R9 RRCC), and circulated via USGS response email list:

    The red tag list has grown to 64 structures. As of 1445 PDT, 25 August, 2014:

    http://cityofnapa.org/index.php?option=com_content&view=article&id=1835%3Ared-tagged-structures-list-as-of-245pm-aug-25&catid=1%3Alatest&Itemid=30

  • huynht
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 7 weeks ago
    Kenneth W Hudnut (USGS) wrote 8/26/14 12:15am:

     

    Latest situation report from FEMA R9. I spoke at length with Jon Bartlett this evening to ensure that critical lifelines operators are aware of the afterslip that has been observed by USGS. He is passing that info along to Don Boland so that all are advised and can perform repairs accordingly.

    Ken Hudnut(626)672-6295
  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 8 weeks ago

    From Fred Pollitz (USGS) responding to Tom Brocher inquire about resurvey of campaign GPS sites near the epicenter: (8/25/14 5:25pm):

    There are 11 campaign stations that we have been re-surveying over the past day and a half. These are shown in the attached figure which I also put on the google drive page. We are discussing re-surveying more stations throughout the area, but the ones given on the figure are the closest to the rupture.

    We do not have results from this campaign yet but hope to soon, and these will be posted online.

    Bill Barnhart has a preliminary `geodetic' slip distribution based on essentially the cGPS results plotted in the figure, which were derived from Jerry's 24 hour time series. Bill's slip distribution has predominantly shallow slip on the northern end of the rupture.

    Fred

  • aemorelan
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 8 weeks ago

    Doug,

    Chad and I were in the field again today to check some measurements and confirm observations from yesterday. We are planning to compile data for distribution tomorrow morning. We will include a summary with lat, lon, and slip in cm.

    Alex

  • eqadmin
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 8 weeks ago

     From Bob Dollar (USGS) 8/24/14 4:39am:

    All,

    I have set up a magnitude counter, using COMCAT, for the Napa area.

    http://tejon.gps.caltech.edu/stats/magcount/nc_napa.php

    Hit refresh to update.

    Surprisingly few aftershocks.

    bob

  • yule
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 8 weeks ago

     Very cool! I will show all of this great information to my class tomorrow on Day 1 of 'Living with Earthquakes in California'. 

  • yule
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 8 weeks ago

    Looks to me like the surface rupture locations are west of the USGS' mapped trace of the (Late Quaternary) fault, and systematically farther away at the north (~50 m) than to the south (~10 m). Is this correct?

  • owen
    2014.08.24 - M6.0 South Napa Earthquake, California   3 years 8 weeks ago

     

    All,

    Posting coseismic GPS offsets (and figure showing horizontal vectors). The pre-event positions are based on 7 days of daily positions. The post-event positions are based on a static solution using ~13.5 hours of data after the earthquake.

    We will monitor subdaily positions to see if GPS sites show additional postseismic movement, especially given reports that surface ruptures have increased significantly since they were first observed. 

    Thanks,

    Sue Owen, Angie Moore, Zhen Liu & ARIA team.