Thanks Alex

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

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Meeting information
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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.)

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

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

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For assistance
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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

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

 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

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 

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

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

 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 

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

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

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