|
Q. How can I find out what sort of earthquake shaking I will be experiencing? Are there maps?
A. Most of Fremont is within 5 km of the Hayward fault and can expect very violent and very strong shaking of Land Level X (10) on the Modified Mercalli Intensity Scale. For more info on earthquakes, go to the ABAG website. View the shaking hazard maps for future earthquakes by City location and by fault on the ABAG website.
Q. What is an Alquist Priolo map?
A. Alquist-Priolo Earthquake Fault Zones (AP) pursuant to Section 2622 of the Public Resources Code are areas designated by the State of California where earthquake fault zones have been mapped, and are referred to as the Alquist-Priolo Special Study Zones. These zones can be as narrow as 600 feet, or as wide as 1500 feet, extending to either side of a known or suspected fault. Within these areas, the ground may be more likely to fracture, or surface rupture, during an earthquake along the particular fault for which the zone is designated. If a property is located within a designated geologic fault zone, a geologic study will be required in Fremont prior to any new or additional construction, and construction requirements may be more expensive. In addition, the availability of insurance and its relative costs could be impacted. The intent of the Act is to prohibit the location of developments and structure for human occupancy across the trace of an active fault. Find more information on the State's website.
Q. Where can I get a copy of the Alquist Priolo maps?
A. The City has copies available at 39550 Liberty Street  in the Development Services Center, 510-494-4443.
Q. Where can I get a copy of the earthquake shaking intensity maps by ABAG?
A. Send to:
ABAG Publications
P.O. Box 2050, Oakland, CA 94604-2050
Phone: 510-464-7900
Fax to: 510-464-7970 (credit card orders only)
Or order on-line at http://store.abag.ca.gov/earthquake.asp
Q. Where can I get a copy of the new State Seismic Hazard Maps?
A. Maps for Fremont are not available yet. The State has released a schedule Summer 2003 for when maps covering Fremont will be released. For more information, please visit the State's website.
Q. The Warm Springs and Mission faults are not on the State Geologist Alquist Priolo maps, so what is the information here?
A. The subject of the Mission Peak Landslide study is primarily a landslide hazard, not earthquake hazards. The 1998 Mission Peak Landslide Study identified the Mission fault and the Warm Springs fault as geologic features within the study area. The State Geologist has not placed these faults on the Alquist Priolo map because there is no physical evidence to show fault surface rupture hazard. This does not mean there are not shaking hazards. The State Map is intended to show surface fault rupture per the Alquist Priolo Act (Ref: http://www.consrv.ca.gov/cgs/rghm/ap/index.htm). It will be updated with the new State Seismic Hazard Maps, which CDMG advises will show these fault traces. Note the new 1997 UBC (Uniform Building Code) fault maps used for structural design show the Mission fault as the Hayward South fault, a Class A fault, (http://gmw.consrv.ca.gov/shmp/) as a step-over feature between the Calaveras fault and the Hayward fault. The Mission and Warm Springs fault traces show seismic activity, but no Holocene era surface rupture. This determination by the State Division of Mines and Geology has implications for new construction or alterations. Locations on the map are approximate and based on research and seismographic recordings on the Mission and Warm Springs fault. The intent of the Mission Peak Landslide map was NOT to locate these fault traces, but to provide area information on their general existence.
Q. I ordered a JCP report and there was no Warm Springs fault mentioned.
A. The JCP report you ordered provided natural hazard disclosures as mandated by State Law. As such, the State Map they consulted and provided you with was the location of faults shown on the Alquist Priolo map previously mentioned. The A-P map does not show the Warm Springs fault. This information will be updated on the State Seismic Hazard Maps when they are released.
Q. What is the current estimate / update on earthquake probabilities?
A. The 2003 U.S. Geologic Survey (USGS) report estimates 62% probabilities of a major earthquake within the SF Bay Area within 30 years, but 27% on the Hayward fault. A Major earthquake is defined as magnitude 6.7 or greater. Learn more information on earthquakes. Learn more information on SFBA predictions.
Q. What is the current forecast for a major Hayward fault quake?
A. The 1996 NCEP (Northern California Earthquake Probability) working group came up with a 210-yr recurrence time for major earthquakes on both segments (northern and southern Hayward fault) which is the same as the best estimate of recurrence of Williams [1993] for the southern Hayward Fault based on trenching data at Tule Pond [TP] in Fremont. The NCEP did not know how the magnitude and length of the 1868 event compares to earlier events, because the paleoseismic record is not adequate to compare the size of events. If the entire 86-km length ruptured with 1.9 m slip, it would be Mw 7.1. Adding the southeastern extension would make it 112 km and Mw 7.2. The NCEP scenario involving the entire length is ranked equally likely. Petersen and others [1996a, b] chose to retain the 1.5 m slip and 167 yr recurrence time adopted by WGCEP [1990] for two Hayward fault segments, that also yields Mw 6.9 and an identical rate of moment release, but they felt it was a more cautious assumption given the great uncertainties in recurrence time. Others have said 197 years plus or minus 60 years.
1868 + 137 = 2005
1868 + 167 = 2035
1868 + 210 = 2078
Take your pick.
Reference: US Geological Survey Open File Report 96-705 - Database of potential sources for earthquakes larger than magnitude 6 in northern California.
Q. What can I do to better prepare for an earthquake?
A. You can educate yourself about earthquakes and their hazards, mitigate structural damage to your facility by consulting with a structural engineer, especially for tilt-up facilities; and prepare your staff. Good information is available in the front of your phone books. The City of Fremont Fire Department also supports Community Emergency Response Teams (CERT).
Back to top.
Q. Why did the Mission Peak landslide reactivate in 1998?
A. This year's reactivation was likely triggered by the unprecedented levels of moisture recorded in this area since January 1993. All-time highs in cumulative rainfall have been recorded during the 1990s, for two, three, four, five and six year periods. This wet sequence was preceded by a 6-year all-time low in cumulative precipitation, between 1986-92 (data presented in Appendix D of Vol. 3)
Q. Can we visit the landslide?
A. No. The City does not consider the grounds reasonably safe to visit. The ground is fissured with cracks and is hazardous to walk on. Additionally, rock fall continues to occur sporadically at the top of the slide. Warning Signs have been placed at the perimeter of the City property at likely access points. Additionally, the hillside has a high potential for grass fires.
Q. How can I get a landslide area designation removed or changed?
A. You will need to perform peer-reviewed special studies using a qualified professional engineering geologist or geotechnical engineer, which would refine the accuracy of the aerial photo mapping. If the study shows the property designation should be revised and the peer review affirms those conclusions, then the City will take steps to record the revision. DO NOT START ANY SPECIAL STUDIES WITHOUT CONSULTING THE CITY FIRST.
Back to top.
Q. Where can I see the local wildfire maps?
A. Fire Hazard Zones are designated in certain areas of the City due to higher exposure to wildfires and limited Fire Department access. All new construction, additions, and re-roofing materials for buildings in this area must be fire-resistive. To find out if a property is located within a Fire Hazard Zone call 510-494-4460. Maps are also available at the Self-Help Center of the City's Development Services Center at 39550 Liberty Street. Generally, the hills east of Mission Boulevard are in the fire hazard zone.
Back to top.
Q. Where can I see sex offender maps?
A. Sex Offender Maps (Megan's Law Maps) - Section 290 of the California Penal code requires people convicted of certain sexual offenses to register with the local law enforcement agency in which they reside within 5 days of their birthday. This is a requirement for the rest of their lives. Maps showing the street names and general location of each offender living in the area are available for review at the Fremont Police Department, or at their website.
Back to top.
Q. Where can I see Dam Inundation Areas?
A. Portions of Fremont, generally the lowlands west of the railroad tracks, are within the dam failure inundation hazard maps for Del Valle Reservoir, Calaveras Reservoir, and Turner Reservoir. These zones are areas where, if one or more nearby dams(s) or dikes(s) fail or overspill, the property could be subject to flooding and/or damages associated with flooding caused by the dam or dike failures(s). There are more than 1400 dams in California - about 75% of these are earthen or rock constructed. Dam failures can be caused by severe earthquakes, or by heavy rainfall resulting in flooding, and overfilling of the reservoir. If the property is located within a Dam Inundation Area, there is currently no requirement for the lending institution to demand flood insurance (as would be the case if the Property were within a FEMA Special Flood Hazard Area). As such, insurance rates will not likely be affected. Detailed maps may be ordered from the California Department of Water Resources Micrographics Dept. at 916-653-6537. These Dam inundation maps were developed in the 1970's to fulfill state law requirements for emergency planning purposes, using engineering hydrology principals, representing a best estimate of where the water would flow if the dam completely failed with a full reservoir. The inundation pathway is based on completely emptying the reservoir and does not include the run-off from storms. Had these maps been developed more recently, different assumptions and map-making methods would have been used. Online version of the map.
Q. Where can I see FEMA Special Flood Hazard Areas?
A. The City has copies available at the 2nd Floor Engineering counter at 39550 Liberty Street in the Development Center. These zones include "Special Flood Hazard Areas" where, in any given year, there is a 1% chance that a portion or all of the property is likely to be inundated by floods, as determined by the Federal Emergency Management Agency Federal Insurance Administration (FEMA). If the property is partially or wholly located within a "Special Flood Hazard Area", the lending institution will likely require flood insurance. The cost of such insurance will be much greater than what would normally be the case. Additionally, governmental restrictions may impact new or additional construction in such a zone. This disclosure pursuant to Section 8589.5 of the Government Code. FEMA also has an online flood map.
Back to top. |
