Questions from the visitors
 


Question 1:
In 1998, at the Geophysical Union Conference in San Francisco, there was a exhibit of a northern Hayward Fault study conducted at a Golf Course in El Cerrito or Richmond.The Study was revealing in that it examined the detritus from a long-established natural pond on the fault line and provided a wealth of historic seismic data.Unfortunately, I took no notes and do not have a clue as to who prepared the Study or where a copy may be purchased.If you know where I may procure same, I would be most appreciative. Better yet, if Memento Mori could reporduce this Study on the Website, everyone would be most appreciative.

Answer:
You are referring to the study conducted by scientists from UC Berkeley and the USGS. The paper at AGU was presented by David Schwartz of the USGS. This trenching work on the northern Hayward fault confirmed an earlier study which indicates that the Northern Hayward fault has not ruptured in a large earthquake since the mid-1700s. Previously, it was believed that the Hayward fault experienced an earthquake in 1836. You will find a press release about this study, as well as other information about the Hayward fault on the Hayward Fault web page: http://www.seismo.berkeley.edu/seismo/hayward/

Question 2:
What is upward and what is downward movement? Or is it just the energy of the movement which is being depicted.

Answer:
The "streaming data" displayed on the Memento Mori site represents the velocity of the ground in the vertical plane, ie - the up and down motion reflects the up and down movement of the Earth's surface at the site near the Hayward fault at UC Berkeley.

Question 3:
I wonder how close Hayward fault lines to Niles Blvd. and Rancho Arroyo Parkway in Fremont near Union City line where I live?

Answer:
The USGS publishes a very detailed map of the Hayward fault, which is available from their office in Menlo Park. Lienkaemper, J., Map of recently active traces of the Hayward Fault, Alameda and Contra Costa Counties, California, USGS Miscellaneous Field Studies Map, Map MF-2196, 1992. For references and links to other maps, please see "Maps of the Hayward Fault" at http://www.seismo.berkeley.edu/seismo/hayward/maps.html.

Question 4:
The site mentions that "The full vertical range of the screen represents 0.0005 mm/s of ground motion." For us folks on the street, what kind of everyday-events that compare to? For instance, roughly what kind of ground motion does a passing truck or bus cause?

Answer:
In general, what you are seeing is what we consider "noise". The sensor is quite sensitive and will record signals generated by storm fronts moving through, by high surf along the coast, by temperature variations from night to day, and by the gravitational tides of the Moon and Sun. You can occasionally see instances where our engineers have gone in to inspect the instruments. In general, however, you are just seeing the response of the Earth. For time to time, you will see an earthquake. I haven't managed to catch one on Memento Mori. But you see examples of these (displayed in a different way) at http://quake.geo.berkeley.edu/bdsn/seismograms.html Since Feb, I think the largest signal was caused by the Balleny Islands earthquake, a magnitude 8.2 event near Antartica. The size of the signal is a function of both the earthquake magnitude and its distance from our recording site. A very small earthquake, right under the station, would probably generate a larger signal. That particular earthquake generated a maximum signal of 2 millimeters/sec. During an earthquake, both the amplitude and the frequency content of the plot will change. The amplitude will probably exceed the bounds of the current plot, so it may be difficult to see the event completely.