Saturday, April 22, 2017

[californiadisasters] 1992 Joshua Tree Earthquake, Sunday, 23 April 2017



"1992 Joshua Tree Earthquake" reminder
When
Sunday, 23 April 2017
06:00 AM to 06:00 AM
(GMT) Greenwich Mean Time - Dublin / Edinburgh / Lisbon / London
Where
Mojave Desert - San Bernardino County
Notes
With the populace of Southern California already on edge from a M4.6 foreshock earlier in the evening during the 7 P.M. hour, this 6.1 earthquake struck at ten minutes to 10 P.M. It severely injured one person and caused tens of millions of dollars in damage, primarily limited to the Yucca Valley area of the Mojave Desert of San Bernardino County. This quake (and the M4.6 foreshock) were located on the Eureka Peak Fault not very far north of the San Andreas Fault Zone (SAFZ) which caused some concern that this might be related to an impending larger quake on the SAFZ. As it turned out this quake was related to an impending larger quake which did strike two months later but to the immediate north along a series of smaller faults and not to the immediate south on the SAFZ. This later larger quake would become known as the M7.3 Landers Quake and the resulting M6.5 Big Bear Quake which struck three hours later, both on the morning of June 28, 1992.
From
californiadisasters   Calendar


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Friday, April 21, 2017

[Geology2] Report identifies grand challenges to better prepare for volcanic eruptions





Report identifies grand challenges to better prepare for volcanic eruptions

April 19, 2017
Credit: National Academies of Sciences, Engineering, and Medicine

Despite broad understanding of volcanoes, our ability to predict the timing, duration, type, size, and consequences of volcanic eruptions is limited, says a new report by the National Academies of Sciences, Engineering, and Medicine. To improve eruption forecasting and warnings to save lives, the report identifies research priorities for better monitoring of volcanic eruptions and three grand challenges facing the volcano science community.

Volcano monitoring is critical for forecasting eruptions and mitigating risks of their hazards. However, few volcanoes are adequately observed, and many are not monitored at all. For example, fewer than half of the 169 potentially active volcanoes in the U.S. have any seismometers—an instrument to detect small earthquakes that signal underground magma movement. And only three have continuous gas measurements, which are crucial because the composition and quantity of dissolved gases in magma drive eruptions. Enhanced monitoring combined with advances in experimental and mathematical models of can improve the understanding and forecasting of eruptions, the report says.

The committee that conducted the study and wrote the report also highlighted the need for satellite measurements of ground deformation and gas emissions, drone observations, advanced seismic monitoring, and real-time high-speed acquisition of data during eruptions. New approaches in analytical capabilities to decipher magma history, and conceptual and experimental models of magmatic and volcanic phenomena, will provide new insights on the processes that explain how magma is generated and erupts.

"There have been great improvements in conceptual models of , compared with those used a few decades ago, but the volcano science community is not yet adequately prepared for the next large eruption," said Michael Manga, professor in the department of earth and planetary science at the University of California, Berkeley, and chair of the committee. "There are fundamental challenges that need to be addressed and require a sustained effort from across disciplines. By working toward these grand challenges, the volcano science community can help quantify the global effect of eruptions and mitigate hazards, ultimately benefiting millions of people living in volcanically active areas."

The committee outlined several key questions and research priorities in areas such as the processes that move and store magma beneath volcanoes; how eruptions begin, evolve, and end; how a volcano erupts; forecasting eruptions; the response of landscapes, oceans, and the atmosphere to ; and the response of volcanoes to changes on Earth's surface.

Based on these research priorities, the committee identified three overarching for advancing volcano science and monitoring:

Annotated aerial photo of Bogoslof volcano on January 10, 2017, showing morphological changes associated with the 2016–2017 eruption. Credit: USGS/AVO

Forecasting the size, duration, and hazard of eruptions by integrating observations with models

Current forecasts are based on recognizing patterns in monitoring data. These approaches have had mixed success because monitoring data do not capture the diversity of volcanoes or their evolution over time. An approach based on models of physical and chemical processes, informed by monitoring data, as is done in weather forecasting, could improve the accuracy of eruption forecasts. Such an approach requires integrating data and methodologies from multiple disciplines, the report says.

Quantifying the life cycles of volcanoes and overcoming our current biased understanding

Current understanding of a volcano's life cycle is skewed because only a small number of volcanoes are studied. Extended monitoring from the ground, sea, and space can overcome some of these observational biases, the report says. Expanding and maintaining monitoring capabilities and supporting the infrastructure to make historical and monitoring data available are critical for advancing understanding of volcanic processes and assessing volcanic hazards. The committee noted that emerging technologies such as inexpensive sensors, drones, and new micro-analytical geochemical methods are promising tools to provide new insights into volcanic activity.

Building a coordinated volcano science community

Close to 100 volcanoes erupt somewhere on Earth each year. Strengthening multidisciplinary research, domestic and international research and partnerships, and training networks can help the research community maximize scientific advances that result from the study of eruptions around the world, the committee said.

The report cites the ongoing eruption at Bogoslof volcano in Alaska as an example that highlights these three challenges. A remote, initially submarine volcano in the Aleutian Island arc, the eruption started in late December 2016 and the activity has been continuing as of February 2017. In just one month, the volcano produced numerous explosions with plumes rising 20,000-35,000 feet, posing a significant hazard to North Pacific aviation. The U.S. Geological Survey Alaska Volcano Observatory (AVO) has been relying on distant seismometers, satellite data, infrasound, and lightning detection to monitor the activity because there are no ground-based instruments on the volcano. The committee said AVO has been able to provide early warning for only some of these hazardous events. This eruption also underscores the limited understanding of magma . In more than 20 discrete events, the emerging volcano has reshaped its coastlines repeatedly, providing snapshots of -landscape interactions.

Explore further: Magma movements foretell future eruptions

Provided by: National Academies of Sciences, Engineering, and Medicine


 https://phys.org/news/2017-04-grand-volcanic-eruptions.html#jCp
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Geology: @1roxxfoxx
Penguins: @wiinterrr
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Posted by: Lin Kerns <linkerns@gmail.com>



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Thursday, April 20, 2017

[Volcano_Vista_HS] VVHS Announcements--Thursday, April 20, 2017



Good Luck to our Hawk band as they prepare for their state competition Friday and Saturday.

 

YEARBOOKS will be on sale next week in A115 at lunch for $70.00.  Buy now. We sold out last year.

 

THE LITERARY MAGAZINE is printed and ready for sale! This year's magazine looks better than ever! For only $5 you can own your very own Literary Magazine which includes poetry, short stories, paintings, and illustrations written and created by VVHS students. Find a creative writing student or visit Ms. Montoya's room in G201 to purchase your copy today. 

 

OPEN MIC NIGHT is almost here! Poets, Musicians, and Dancers get ready to perform on April 28th from 6:00-9:00 in the black box. The cost is $5. The sign-up sheet will be in Mr. Zimmerman's room, H115 beginning on April 24th.  Can't wait to see you there!  

 

THE VOLCANO VISTA GAY STRAIGHT ALLIANCE is sponsoring the Day of Silence this Friday, April 21. The mission of the Day of Silence is to raise awareness of the silencing effect of anti-LGBT bullying, harassment, and discrimination.  We are inviting all members of the Hawk community to sign up and participate.  We will have sign up stations in the eateries during lunch on Wednesday and Thursday, and we will also have a sign up station in the mornings before school in A-hall.  Remember, strength in numbers, solidarity in silence.

 

COUNSELING:

  • The FBI Albuquerque Division is accepting applications for its Teen Academy, which will run June 21-23, 2017.   Applications must be received by 5 p.m. Wednesday, April 26, 2017.   The FBI Teen Academy gives rising 11th and 12th graders an opportunity to learn about today's FBI. Classes are free, run six to eight hours daily and will be held at the Albuquerque field office. Candidates must be in the 11th or 12th grade for the 2017-18 school year, and will be required to send a transcript, complete an application, and write an essay. Anyone wanting more details and an application should send a request to aq.outreach@ic.fbi.gov.

  • Seniors:  Please check the fines list posted outside the bookroom and pay Ms. Brown in the bookroom by May 12th.

 

ATHLETICS:

  • TENNIS: Metro tennis is this week.   

 

And remember

As always

It's Great to be a Hawk!



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Posted by: ssteckbeck@yahoo.com


For more information, go to our web site: http://www.volcanovistahawks.com




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Wednesday, April 19, 2017

[californiadisasters] On This Date In California Weather History (April 19)



1988: Heavy rain began on this day and ended on 4.23 (SoCal).
4.15" of rain fell in 24 hours at Mt. Wilson.
Flooding, mud slides and numerous traffic accidents occurred around LA.
26 were injured in a major collision.
Three straight Dodgers baseball games were rained out.
Only 12 rainouts had occurred in the previous 26 years.

1983: Heavy rain that started on 4.17 and ended on 4.20 caused street flooding and mud slides.

1981: The Angels' home game at Anaheim Stadium against the Minnesota Twins was rained out.

1968: It was 34° F in Palm Springs, the lowest temperature on record for April.

1967: Two day snowfall from the 18th-19th of 32" in Yosemite Valley.

1963: Funnel clouds were observed near Fresno.

1906: Santa Cruz had a high of 90° F. 

Source: NWS San Francisco/Monterey, Hanford, & San Diego

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Posted by: Kim Noyes <kimnoyes@gmail.com>


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[Geology2] Tsunami Record from the Great 1906 San Francisco Earthquake



 

Tsunami Record from the Great 1906 San Francisco Earthquake

An Unusual Tsunami

Shortly after the Great San Francisco earthquake of April 18, 1906, a sea level disturbance (tsunami) was recorded at the Presidio tide gauge station in San Francisco (the station is now located nearby at Ft. Point). This disturbance puzzled Lawson (1908), author of the comprehensive report of the earthquake, and Henry Reid, proponent of the elastic rebound theory of earthquakes, primarily because it appeared as a small and solitary negative amplitude wave. Here is what the record looked like with the tidal component removed (the red arrow indicates the approximate time of the earthquake):

Tsunami Record

This tsunami record is unusual because the initial lowering of sea level is not followed by a subsequent positive amplitude wave. The lowering of sea level over about 16 minutes was followed by a series of oscillations with an approximate period of 40-45 minutes. Lawson (1908) originally ascribed these later oscillations to reverberation of the tsunami within San Francisco Bay. As shown in the animations below, however, it appears that these oscillations are caused by complex wave effects outside the Golden Gate and not within the bay. The central question remains--what type of mechanism (earthquake rupture, landslide, other) generated the tsunami recorded at the Presidio tide gauge station.

New Fault Interpretation

High-resolution aeromagnetic data was collected to better illuminate the geometry of the San Andreas fault offshore of the Golden Gate. Interpretation of the data by Jachens and Zoback (1998) and Zoback et al. (1999) indicated that the San Andreas fault makes a 3 km right step north of Lake Merced and a smaller 1 km left step south of Bolinas Lagoon, as shown by the red line in Figure 1 below:

Figure 1
San Andreas Mapmetadata

We can further test the hypotheses that rupture of the San Andreas fault during the 1906 earthquake occurred (1) on the newly defined discontinuous fault segments or (2) on a continuous fault trend defined by the older interpretation (orange line in the figure above). At the same time, we must consider other non-seismogenic sources for the tsunami, including massive cliff failures caused by the ground shaking as reported by Lawson (1908).

The Tsunami Model: A Convergence of Disciplines

Geologic investigations in the San Francisco Bay region are, of course, not limited to earthquake studies. The USGS has a vigorous research program related to environmental aspects of San Francisco Bay. (See Access USGS San Francisco Bay for a complete overview of research.) As part of the broader effort, researchers from the Water Resources Division of the USGS have develop an estuarine circulation model to study sediment and pollutant transport in the bay. The hydrodynamic model used for environmental studies is modified to model tsunami propagation, using initial sea level conditions specified by the parameters of earthquake rupture. Slip during the 1906 earthquake is resolved from geodetic measurements before and after the earthquake (Thatcher et al., 1997):

Figure 2
Slip Distribution

Aside from the amount of slip during the earthquake, we need to specify parameters that describe the geometry of faulting. Two of the cases tested include a tsunami generated from continuous rupture of the fault represented by the green line in Figure 2 (orange line in Figure 1) and discontinuous rupture indicated by the new interpretation. The calculated subsidence of the earth's surface for the two cases is shown below:

Subsidence and Synthetic, 1Subsidence and Synthetic, 2

metadata

Below each figure we show a section of the tide gauge record (solid line) in comparison with a synthetic record using the assumed source geometry. The tsunami record is consistent with rupture of discontinuous segments of the San Andreas fault along the Golden Gate platform. Using this hydrodynamic model, we test other possibilities such as compound rupture involving nearby faults in addition to the San Andreas and tsunamis generated by cliff failures. Of all the possibilities, discontinuous rupture of the San Andreas (above) seems to best explain the Presidio tide gauge record.

Animation of the 1906 Tsunami

The results above indicate the tsunami from the 1906 San Francisco earthquake was caused primarily by downdropping of the sea floor north of Lake Merced, between overlapping segments of the San Andreas fault. Three observations are apparent from hydrodynamic modeling of this tsunami: (1) the tsunami propagated from the source region to the Golden Gate as a trapped wave (i.e., a particular class of waves that propagate parallel to the shoreline); (2) trapped waves generated by this earthquake were reflected and scattered, resulting in the 40-45 min. period oscillations apparent on the tide gauge record; (3) relatively little wave energy is transmitted through the Golden Gate to San Francisco Bay.

Below are snapshots of the tsunami derived from the discontinuous fault model described above (black lines are current vectors located at every model grid point spaced 250 m apart).

Snapshots of Tsunami

The animation is available at two horizontal scales:

small scale animation (centered near the Golden Gate)

large scale animation (covering the San Francisco Bay region)

Concluding Remarks

In hindsight, it is remarkably fortuitous that a tsunami was recorded from the 1906 San Francisco earthquake. First, the most likely epicenter for the earthquake was located within 15 km of the only tide gauge station operating in northern California at the time. Second, if the San Andreas fault was continuous offshore, a tsunami probably would not have been recorded. The fact that the San Andreas fault makes a right step in the offshore region means that during earthquake rupture the sea floor is downdropped in the stepover region, resulting in the generation of a tsunami. It is evident from this study that tide gauge records can provide additional and corroborating information on the rupture process of historic earthquakes.

Even though the magnitude of the 1906 earthquake was large (M 7.8), it generated a tsunami wave only approximately 10 cm in height. In contrast, a tsunami from a similar magnitude subduction zone earthquake in other regions bordering the Pacific basin would have (on average) generated a much larger tsunami. The primary tsunami threat along the central California coast is from distant tsunamis generated by earthquakes along subduction zones, such as the 1964 Great Alaska earthquake. For more information on tsunami inundation maps, see the National Center for Tsunami Research.

Source: https://walrus.wr.usgs.gov/tsunami/1906.html


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Posted by: Kim Noyes <kimnoyes@gmail.com>



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[Geology2] Huge asteroid to zip 'near' Earth on Wednesday



Huge asteroid to zip 'near' Earth on Wednesday

, USA TODAY Published 3:26 p.m. ET April 18, 2017 |

It's a near-miss in space terms.

A 2,000-foot-long asteroid, almost twice the size of the Rose Bowl, will zip safely past Earth on Wednesday at a distance of about 1.1 million miles, about 4.6 times the distance from Earth to the moon.

Although there is no possibility the asteroid, with the ungainly name of 2014 JO25, could collide with our planet, it will be a very close approach for an asteroid of this size, NASA said.

"Close is kind of a relative term," AccuWeather meteorologist Brian Lada said. "The closest it's going to be to the Earth is more than a million miles away."

It's the closest this asteroid has come to Earth for at least the past 400 years and will be its closest approach for at least the next 500 years.

NASA said the approach is the closest by any known asteroid of this size since the 3.1-mile-wide asteroid Toutatis approached within about four lunar distances in September 2004. Not until 2027 will we have another shot at seeing a big rock tumble so close by, Sky and Telescope said.

The asteroid is so massive that astronomy website Slooh.com nicknamed it after popular movie star Dwayne Johnson, aka The Rock.

The flyby should also be visible with amateur telescopes, beginning in the early morning hours on Wednesday and then again that night, according to EarthSky.org. Wednesday morning, it can be spotted in the northern sky near the constellation of Draco.

Wednesday night, asteroid 2014 JO25 will pass though the constellations Canes Venatici and Coma Berenices in the eastern sky.

The asteroid was discovered in May 2014 by astronomers at the Catalina Sky Survey near Tucson, Ariz.

Source: https://www.usatoday.com/story/tech/sciencefair/2017/04/18/huge-asteroid-zip-near-earth-wednesday/100607294/


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Posted by: Kim Noyes <kimnoyes@gmail.com>



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Tuesday, April 18, 2017

[californiadisasters] On This Date In California Weather History (April 18)



2004: No measurable rain fell in San Diego on this day, starting a streak of 182 consecutive days of no measurable rain, the longest dry streak on record.
The last dry day in the streak was 10.16.

2000: A storm that started on 4.17 and ended on this day brought up to 2" of rainfall to lower elevations and 18" of snow to Wrightwood.
Winds gusted to 68 mph in the mountains of San Diego County.
A severe thunderstorm brought downburst winds estimated at 80 to 100 mph from Bellflower to Diamond Bar. 0.75" hail was reported in Downey.
The storm left severe damage to factories and mobile home parks in Paramount (one mobile home was blown over).
Wind damage was done to trees, power lines and numerous buildings along the entire path.
A large Eucalyptus fell over I-5, closing the freeway for three hours.

1991: Wind gusts of up to 50 mph caused blowing dust that dropped visibility to near zero parts of in Merced County.

1987: High winds in Las Vegas, NV, blew down billboards and power poles.
77 mph gust at Desert Rock. 

1983: Heavy rain that started on 4.17 and ended on 4.20 caused street flooding and mud slides.

1967: 16" of snow fell at Tahoe City (west shore Lake Tahoe).

1967: Hail and gusty winds damaged and destroyed grape and plum crops (San Joaquin Valley).

1961: Salinas had a low temperature of 35° F. 

1956: Heavy thunderstorms struck Barstow and Victorville with an estimated 1.25" of rain.
0.25" hail was also reported covering the ground.
A wall of water two feet deep damaged 40 homes in west Barstow.

1955: Around 3PM a thunderstorm dropped hail near Biola as large as ¼ inch in diameter and left a path 3 miles long and about 1 mile wide damaging some crops.
Just an hour earlier, a tornado (no Fujita rating) was reported in Merced County.

1949: A tornado was reported in Reno, NV.

Source: NWS San Francisco/Monterey, Hanford, Reno, Las Vegas, & San Diego

--


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Posted by: Kim Noyes <kimnoyes@gmail.com>


Be sure to check out our Links Section at http://groups.yahoo.com/group/californiadisasters/links
Please join our Discussion Group at http://groups.yahoo.com/group/californiadisasters_discussion/ for topical but extended discussions started here or for less topical but nonetheless relevant messages.





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