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Perspective View of Mw 6.0 ~ 6.1 South Napa Earthquake,Calif

 
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sikandarsiddiqi
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PostPosted: Wed Jan 28, 2015 6:58 am    Post subject: Perspective View of Mw 6.0 ~ 6.1 South Napa Earthquake,Calif Reply with quote

IN GOD WE TRUSTPARDON,PROTECT & HELP US LORD, GOD GIVE US THE WISDOM TO UNDERSTAND YOUR WAY OF CREATION WHICH WE CALL SCIENCE,TO BE EXPERT NEEDS PRACTICE & SELF IMPROVEMENT, LETS PRAY FOR ALL THOSE WHO ARE SICK FOR EARLY RECOVERY & IN DISTRESS,HELP SOME ONE IN POVERTY LEVEL  Dear Colleagues,Friends & Others > Worldwide:
The San Andreas Fault runs roughly 810 miles along the Pacific coast line west of California.Its motion is right lateral strike slip. The fault divides into three segments, each with different characteristics, and a different degree of earthquake risk. Although the most significant southern portion segment dates back to near about 5 million years, the oldest sections were formed by the subduction of a spreading ridge 30 million years ago.The fault lines listed on the right in technicolor along with the main San Andreas Fault is called the San Andreas Fault System (SAFS).Another fault line exists of similar nature in Turkey which is the North Anatolian Fault about 745 miles long, and stretches from northern Turkey to the Aegean Sea. An analysis of 20 years GPS data along the fault shows due to seismic gap under the Sea of Marmara at Princess Island, just 5 miles west of Istanbul a major earthquake ranging in between 7 to 8 on the Richter scale within next 25 to 30 years is likely.So alarming for Istanbul indeed and also within a radius of 125 miles.Pls See the map below :It has been known that earthquakes on this fault tend to follow a successive sequence, i.e. an earthquake rupture will often occur in the section of the fault proceeding the last rupture. The current sequence started in 1939 with the magnitude 7.9 Erzincan earthquake and has been progressing to the west in a series of 12 large earthquakes.
Researchers in 1997 used this observation to successfully predict the location of the 1999 Izmit earthquake but not the exact time. The Izmit earthquake ruptured less than 100km to the east of Istanbul.

North Anatolian FaultDamaged Building : 19th May 2013 earthquake,Turkey.
                                                                                                                                                                                                                                                                                        Istanbul,Turkey,is a city of major empires including the Roman, Byzantine, Latin and Ottoman.At present It is a city of more than 15 million people.
A building destroyed in the 1999 Izmit earthquake

Istanbul is near the North Anatolian Fault which is the most active fault system in Turkey and the source of the 1999 M 7.4 Izmit earthquake.

It has been known that earthquakes on the fault tend to follow a successive sequence, i.e. an earthquake rupture will often occur in the section of the fault proceeding the last rupture. The current sequence started in 1939 with the magnitude 7.9 Erzincan earthquake and has been progressing to the west in a series of 12 large earthquakes.
Researchers in 1997 used this observation to successfully predict the location of the 1999 Izmit earthquake but not the exact time The Izmit earthquake ruptured less than 100km to the east of Istanbul. Further work has led other researchers to predict a major earthquake, possibly another magnitude 7.4 or above near Istanbul within the next 25~30 years.
In the map given below West Napa Fault has been marked yellow for position detection.Please note that all fault lines are approximately parallel,therefore,easy stress transfer when one is activated.There are other known & unknown mini fault lines within and near by in the entire area that is to say a fault line network system (FLNS).   Map of the San Andreas Fault showing relative motion




IMPORTANT : Click over the USGS earthquake map to see the names of the fault lines that look like a network. Zoom in and click on the South Napa quake for more specific location.View a full-screen version of the map by a click on here.(Pls study this seismic map to know more)At 3:20 AM local time on 24th Aug'14, the northern San Francisco Bay Area was struck by a damaging earthquake since 1989 M6.9 Loma Prieta quake.Earthquake appears to have ruptured on the West Napa Fault which the USGS has named as “South Napa earthquake.” It was the biggest quake in last 25 (twenty five) years.West Napa Fault is 27 miles long from the city of St. Helena south to the American Canyon. It was a strike slip earthquake.The surface ruptures show a northward shift west of the West Napa fault of about 5 cm (2 inches).Modern buildings are earthquake resistant and many buildings are retrofitted including some old structures but then why so much damage? I shall give the answer within the content of this text.Earthquake also caused landslides and liquefaction contributing to damage.Message received from USGS suggests:Region: NORTHERN CALIFORNIA > Napa ValleyGeographic coordinates: 38.214N, 122.319W 0.2 kmMagnitude: Mw 6.0 ~ 6.1Depth: 10 km 0.2 km

Number of Stations Used :146Universal Time (UTC): 24 Aug 2014 10:20:44Time near the Epicenter: 24 Aug 2014 03:20:44Local standard time in your area: 24 Aug 2014 10:20:44Event ID : nc72282711Epicentral Distance (ED):6 km (3 mi) NW of American Canyon, California9 km (5 mi) SSW of Napa, California13 km (8 mi) NNW of Vallejo, California14 km (8 mi) SE of Sonoma, California82 km (50 mi) WSW of Sacramento, CaliforniaFault map suspected in Napa quake :                                                                                                                               
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A statewide assessment six years ago of major earthquake risks, for example, did not mention the 27-mile-long fault, which runs through the hills west of Napa as Bay Area earthquake fault lines go,the West Napa Fault—tentatively identified as the source of Sunday’s magnitude 6.0~6.1 quake is a relative stranger hit hard by the quake at 3:20 a.m.But the West Napa Fault runs just 4 miles east of the Rodgers Creek Fault, which struck Santa Rosa in October 1969 which prompted Sutter Medical Center to build a new hospital.
M 6.0~6.1 quake in Napa, California,involved a previously unknown active fault lines as well as faults that were thought to be inactive. The quake caused widespread damage that may total several billion dollars and revealed new movements in 1.6 million year old faults.Ruptures on the surface are now helping scientists map these fault lines that are shedding insight into the area's earthquake risk exposure. City officials in Napa had long worried about possible damage of historic brick-walled buildings (brick walled buildings also exist in Seattle exposed to Cascadia Subduction Zone Earthquake) by a major earthquake if any.For example the three-story 104-year-old Alexandria Square building was retrofitted but failed. In my opinion California Seismic Safety Commission(CSSC) simply under estimated the probable intensity level on MMIS because a nationwide assessment six years ago of major earthquake risks did not mention this 27-mile-long fault, which runs through the hills west of Napa but now faced an earthquake of level VIII on MMIS.So,you can well imagine the degree of damage that occurred. As earthquake is probabilistic physics,so nothing can be guaranteed.Due to stress transfer or some other tectonic reason dormant fault lines may become active triggering damaging quake depending upon the magnitude,focal depth and soil condition.So in my opinion,further, earthquake zonation map and microzonation are misleading if real time situation is taken into account as there are lot of similar damaging earthquakes around the world over last few years including Sichuanprovince of China which is evident from the scale of devastation and so is the case with Christchurch,New Zealand & very recent  Orkney,South Africa earthquakes.2008 M8.0 Sichuan province earthquake of China was felt all over Bangladesh.So in view of the above real time out put of earthquake zonation and microzonation maps my recommendations for earthquake risk areas ( strike slip & subduction interface ) around the world are as follows to minimize structural damage and loss of lives :a) Imperial Mogul brick-walled structures,built through out Mogul Empire and similar type constructions in Central Asia including Dhaka,Bangladesh,have survived all major earthquakes.Kutub Minar in Delhi was damaged but minars of  Tajmahal Mahal remained intact.So the seismic cause be studied and transformed into equivalent modern earthquake proof construction.b)  Abolishing earthquake zonation & microzonation maps for earthquake risk areas such as Bangladesh,India,Indonesia,U.S.A.,New Zealand and elsewhere in the world, soil condition based unified standard  be followed for construction of earthquake proof building.If this is done the building will be safe in real time  situation. This earthquake proof design philosophy is as follows: :  1. For soil whose ultimate bearing capacity is in between 5 to 6 ton per sft the intensity level be taken as VII (7) on MMIS with a factor of safety 2.If this is done the building along with lives & assets will be safe in real time situation.  2. For soil whose ultimate bearing capacity is in between 3 to 4 ton per sft the intensity level be taken as VIII (Cool on  MMIS with a factor of safety 2.If this is done the building along with lives & assets will be safe in real time situation.  3. For soil whose ultimate bearing capacity is less than 3 ton per sft the intensity level be taken as IX (9) on MMIS with a factor of safety 2.If this is done the building along with lives & assets will be safe in real time situation. Please note with attention why factor of safety 2 ? This is necessary for absolute seismic safety to take care of epicentral hazards due to sudden activation of known or unknown faults including earthquake swarms having focal depth in between 10 to 15 km any where in earthquake risk zone.Recipients of this email: Please reply with comments if any as this is a very important issue.Two quotes : The mitigation of earthquake risk requires the knowledge of hazards to be delivered to the people that need it.
~Professor Roger Bilham,World Famous Seismic Scientist
Monday 8th September 2014


We cannot eliminate disasters but we can mitigate risk. We can reduce damage and we can save more lives.
~Mr.Ban Ki-Moon, United Nations Secretary General
Monday 1st September 2014

Our top most priority is seismic safety,no compromise,in all respects whatever may be the over cost beyond normal to avoid loss of lives.Re-construction of a collapsed building,compensation and the cost of human lives lost together will be far more greater than the cost of an earthquake proof building in real time situation.After all we must work for the benefit of mankind.

It’s not just older,non-retrofitted buildings that suffered significant damage during 6.0 ~ 6.1 quake but also some recent constructions as well in Napa due to wrong estimate of the probable maximum value on MMIS (Modified Mecalli IntensityScale),note the above bold typed text.
Population Exposure per 1 sq. km :
List of cities exposed are given below along with intensity felt on Modified Mercalli Intensity Scale (MMIS) (depending on ground density condition) with 1,000 or more population with reference to GeoNames Database.
MMISCityPopulationVIIINapa77k (5 miles from epicenter)VIIYountville3kVIIAmerican Canyon19k (3 miles from epicenter)VIEl Verano4kVISonoma11k (8 miles from epicenter)VITemelec1kIVOakland391kIVSan Francisco805kIIISacramento466k (50 miles from epicenter)Instrumental Intensity : California Integrated Seismic Network(CISN)
M6.0 earthquake caused significant damage in south Napa County ( images given below).It occurred in the broad zone of deformation that accommodates the relative motion of the North American and Pacific Plates.The Earthquake Early Warning system functioned as designed and within five seconds of the earthquake it produced a warning, sufficient to provide warning to Berkeley, San Francisco, and areas farther south. No warning would have been possible within 20 miles of the earthquake.EEW prototype was developed by the USGS in partnership with the UC Berkeley, California Institute of Technology, University of Washington, and the Gordon and Betty Moore Foundation.
Image : CNN > Napa 5 miles from epicenter,MMIS level VIII  Image : CNN > Napa 5 miles from epicenter,MMIS level VIII Image : CNN > Napa 5 miles from epicenter,MMIS level VIII Image : CNN > Napa 5 miles from epicenter,MMIS level VIII Image : CNN > Napa 5 miles from epicenter,MMIS level VIII Image : CNN Napa 5 miles from epicenter,MMIS level VIII Image : CNN > Napa 5 miles from epicenter,MMIS level VIIIThis quake damaged more than 800 buildings and till now more than 100 buildings were red tapped i.e unsafe to enter as likely to collapse,near about 500 buildings were marked yellow as unsafe to live in.Detailed survey may alter this figure.M5.0 Yountville earthquake of the year 2000 occurred on the West Napa Fault and also damaged Napa. The1898 M6.3 Mare Island earthquake occurred in the vicinity of 24th Aug'14 earthquake.
Damage is localized in the region surrounding Napa due to the rupture directivity to the north-west. River valley sediments in Napa zone has amplified the PGA value there by causing significant damage.

USGS and California Geological Survey (CGS) geologists mapped surface rupture produced by the earthquake from the epicenter NNW at least 10 km (6 miles) on a previously mapped strand of the West Napa Fault.At that point the surface rupture may have shifted eastward about half a mile toward Napa and extended NNW another few miles along a previously unmapped strand of the West Napa Fault. USGS and CGS geologist continue to conduct field reconnaissance to refine these interpretations and to look for additional surface rupture.The surface ruptures show a northward shift west of the West Napa fault of about 5 cm (2 inches).
GPS receivers operated by the USGS and others also measured a shift of the earth of a few inches caused by the earthquake.

USGS analysis of the seismic recordings indicates the earthquake rupture propagated to the NNW and upward, directing the brunt of the earthquake energy to the NNW towards Napa. The dozens of aftershocks that have been recorded to date are also aligned on this NNW trend.

USGS technicians will be retrieving additional seismic data from several seismic stations and will also be deploying additional recorders in Napa. These data should help refine the Shake Map showing the intensity of shaking throughout the Bay Area.

The Earthquake Early Warning system functioned as designed and within five seconds of the earthquake it produced a warning, sufficient to provide warning to Berkeley, San Francisco, and areas farther south. No warning would have been possible within 20 miles of the earthquake.EEW prototype was developed by the USGS in partnership with the UC Berkeley, California Institute of Technology, University of Washington, and the Gordon and Betty Moore Foundation.The Pacific Tsunami Warning Center(PTWC) is also helping UC Berkeley in its earthquake early warning system.
Five seconds after the quake hit Napa Valley,California, the alarm started ringing at the Pacific Tsunami Warning Center in Ewa Beach,Hawaii.Normally it takes minute or two.PTWC can issue a tsunami warning in two to three minutes, instead of five, in case of a tsunami triggering quake.The area surrounding the epicenter of the mainshock is continuing to experience a number of aftershocks. As of Tuesday Aug. 26, 4 PM PDT, there have been more than 100 aftershocks; only three of these have had magnitudes greater than 3.
  • M3.0 Tuesday 6:45 AM PDT
  • M3.9 (largest aftershock) Tuesday 5:33 AM PDT
  • M3.6 Sunday 5:47 AM PDT
  • M3.5 (4 minutes after mainshock) Sunday 3:24 AM PDT
Stress transfer is most likekly to the Hayward fault which runs to the east of San Francisco Bay is now over due for a major quake. Its last earthquake was in 1868, almost 150 years ago. The past five large earthquakes on the Hayward fault were 140 ~ 155 years apart.The additional pressure due to stress transfer on the Hayward fault is 0.5 bars or about a fifth of the pressure of car tyres,This fault has a probability of rupturing in the next 20 ~25 years.The USGS estimates that there is a 1 in 3 chance of M6.7 or larger quake on the Hayward fault by 2037. Such an event would be devastating to San Francisco, Berkeley and people living in the Bay Area depending on timing of the quake,therefore,the Government of the United States of America must under take immediate Seismic Evaluation & Retrofitting for seismic safety.Click on section to view enlargements Iceland,Chile,Peru & California, around the world, are struck by abnormal number of major earthquakes this year,2014.
Catastrophic earthquakes seem to strike along the southern San Andreas Fault about once every 150 years,focusing studies of past 1,400 years. The last time a major quake struck Southern California was in 1857.But the San Francisco Bay Area is less likely to see a major earthquake soon, as only a century has passed since the great 1906 earthquake,but potentially damaging earthquakes may occur at any time as earthquake is a probabilistic physics.
The San Andreas Fault is responsible for 1906 the Great San Francisco earthquake.The 810-mile-long fault is the boundary between the Pacific Plate and North American Plate.The Pacific Plate shifts about 2 inches a year (5cm).Professors & Vice Chancellors around the world receiving this mail are requested to display a print of this on the notice board because of academic nature of the text.Please also forward this email to your friends & colleagues as well.With this much now signing off.Regards & Best Wishes.Blessings of Almighty God be upon all of us.Sincerely,Engr.Sikandar Hayat Siddiqi Director General & Principal Scientist,Earthquake & Tsunami Safety Management Initiative (ETASMI)/ Chief Technical Co-ordinator,ETASMI Data Center/Chief Executive Officer, ETASMI Information Service /Project & Seismic Design Management Consultant / Earthquake Public Awareness Consultant/Earthquake
Our Ref : ETASMI/Napa Eq/24th Aug'14 Dhaka  Bangladesh/Asia Radio Link International Email12:58 PM Dhaka Time,Wednesday,28th Jan'15 + 6 Hours GMT

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