3/20/16: LANDSLIDES IN CA

Landslides impact California’s terrain often. These are generally related to precipitation patterns, in particular if there has been previous months of drought conditions. In 1982, a series of landslides near San Francisco killed 33 people and closed the Golden Gate Bridge. A total of 18,000 different landslides took place in the San Francisco Bay Area following a very heavy rain storm (data collected by aerial surveillance in the days following the event). Two fast-moving fronts carrying extremely heavy rain passed through in a 36-hour period, during which the area received an amount of rain equal to half its average annual precipitation. 

Another famous unstable area is La Conchita. A mudslide of 400,000 tons of mud in 2005 killed 10 people. This should not be surprising as the exact same place suffered another hill collapse in 1995, destroying 9 homes. In that occasion, the landslide consisted of 600,000 tons of mud and silt slid 600 feet down a cliff face (see topo map in the figure. Note all houses are built donwlope of a very steep slope...).

The obvious approach is study well the soil in where we put homes and also learn from previous occurrences, understanding that areas that are unstable will continue being so  (La Conchita is not alone; Oso area had been unstable before the 2014 event).  Detailed geologic reports have been made in the past of these places, but the personnel that has the power to act have not followed up/ignored them or have not read them. Gravity always wins. We know better?

After the 2005 disaster, there was an attempt of a $50-million grading project. There were also calls for the county to buy up all the homes through eminent domain and never allow anyone to live there again. It was an idea that came and went, as was the grading project.

There is a USGS page with information on how to identify landslides and what to do if one happens: http://landslides.usgs.gov/learn/prepare.php

http://www.history.com/this-day-in-history/landslides-kill-33-in-california

http://www.usgs.gov/blogs/features/usgs_top_story/rain-and-landslides-in-california/

http://www.latimes.com/local/california/la-me-la-conchita-20150104-story.html#page=1

http://pubs.usgs.gov/of/2005/1067/508of05-1067.html

http://www.geog.ucsb.edu/~jeff/projects/la_conchita/apcg2001_article/apcg2001_article.html

2/29/16: Minimizing Volcanic Hazards: USGS Alert Codes

This week Geol9 is exploring the volcanic hazards in different countries and their warning systems. I’ll be focusing on the US.

There are several ways we minimize the danger of volcanic activity (apart from the obvious of ‘getting out of the way’…(J:

• ·   Forecasting (earthquakes as early warnings -although in 2014 a Japanese volcano erupted without any previous seismicity (livescience article), land swelling before eruption, gas emissions, etc.)
• 
  
• ·  Volcanic Alert Codes (USGS): the levels of alert and the aviation code levels commonly change at the same time. A non-erupting volcano will have a green icon, and a red one indicates an imminent eruption (see USGS Alert Codes).

Today the US hazards map shows the following U.S. volcanoes as to be above normal background (elevated unrest or eruptions) or have shown activity that warranted an Information Release (for example, an earthquake swarm):

Shishaldin, Cleveland, Mauna Loa Alert Level=ADVISORY. Aviation Color Code=Yellow.

Kilauea Alert Level=WATCH. Aviation Color Code=Orange. 

Note: this one has been erupting for 33 years! (see more here).

More information @

http://www.volcanodiscovery.com/news.html

http://volcanoes.usgs.gov/vhp/updates.html

http://www.wired.com/2016/01/keep-an-eye-out-for-these-volcanoes-in-2016/

All for now-

2/14/16: Only For Quake Lovers: Exploring Seismicity and Mitigation Strategies

If I want to know something about earthquakes, the first websites I go to are: the USGS Real Time Earthquakes Website or the IRIS monitoring website.

This week we are exploring seismicity and what countries do to prevent/mitigate the hazard.

Re: the first issue, the new 2014 US map of seismicity (see image from USGS) shows the (obvious, in pink) ring of fire portion on the West coast but also a central area in the middle of the plate. I’d like to talk a bit more about this non-obvious one. This area, called the New Madrid Zone was shaken by a M8(!) in 1811. The reason for the activity is a very old intraplate rift placed below the area (see image from http://showme.net).

A great new blog post summarizes nicely the Cascadia subduction Zone dangers....

Re: the second issue, I want to focus on a brand new effort by the USGS: the ShakeAlert system, developed for the West coast using some of the existing systems. Today, the technology exists to detect earthquakes, so quickly, that an alert can reach some areas before strong shaking arrives. The purpose of an EEW (Earthquake Early Warning) system is to identify and characterize an earthquake a few seconds after it begins, calculate the likely intensity of ground shaking that will result, and deliver warnings to people and infrastructure in harm’s way. Studies of earthquake early warning methods in California have shown that the warning time would range from a few seconds to a few tens of seconds, depending on the distance to the epicenter of the earthquake. 

A few seconds of warning might make all the difference (enough to stop transit/elevators and to drop, cover, hold on). All for now-

2/7/16: Introduction to Geological Activity at Plate Tectonic Boundaries

This week we are exploring plate tectonics and how the location of each country is affected by its position respect to plate boundaries.

The NOAA map shows clearly how the Easter US is a passive margin and the Western side of the country is a very active one, with the Pacific Plate, Cocos, Juan de Fuca plates connecting to the North American plate. Not a surprise we are on the ‘Ring of Fire’, where a lot of the volcanic and seismic activity happens!

Of course, there are a few exceptions, like the activity of Hawaii (hot spot) or the New Madrid area (ancient rift), both not at plate boundaries, but is for some other time.

We might not know when events like volcanic eruptions or big earthquakes will happen, but if you know your Tectonics, you definitely know where the do!

Other interesting Plate Maps can be found at USGS or Esri: interactive. All for now-

11/16/15: COASTAL HAZARDS IN THE US

The National Assessment of Coastal Change Hazards of the USGS has very good information about coastal issues in the country.

Also, the USGS Coastal Change Hazards Portal is a new tool that allows anyone to explore how coasts change due to: extreme storms, shoreline change, and sea level rise.

Extreme Storms: this allows ‘real-time and scenario-based predictions of storm-induced coastal change, as well as the supporting data, are provided to support management of coastal infrastructure, resources, and safety.’ For example, let’s focus on the Gulf Coast and a scenario of a hurricane (any category). Let’s see how a Cat 1 and a Cat 5 possibly looks like (with probabilities of collision (dune erosion), overwash, and inundation for sandy beaches along the Gulf and Atlantic coasts during a generalized hurricane landfall): see figures for both. The most probable areas should be risks areas and treated as such in an emergency.

Shoreline Change: this shows: ‘historical shoreline positions and rates of change along ocean shorelines of the United States’. Looking into the East coast now, offshore Norfolk, see figures for long-term coastal change rates, and for the short-term rates (<30 years rates of shoreline change for open-ocean shorelines of the United States ranging from 1970's to 2001).

Sea level Rise: there are two methods used to address this: a Coastal Vulnerability Index (CVI), and a probabilistic assessment of shoreline change. 

CVI: ‘a preliminary overview, at a National scale, of the relative susceptibility of the Nation's coast to sea-level rise through the use of CVI. This classification is based upon the following variables: geomorphology, regional coastal slope, tide range, wave height, relative sea-level rise and shoreline erosion and accretion rates. The combination of these variables and the association of these variables to each other furnish a broad overview of regions where physical changes are likely to occur due to sea-level rise’. A quick image shown here shows how much red (very high vulnerability) our California coasts possess.

Probabilities of Shoreline Change: ‘this dataset was used to develop and evaluate the performance of a Bayesian network (BN) that predicts long-term shoreline change associated with sea-level rise. The BN is used to define relationships between driving forces, geologic constraints, and coastal response, which includes observations of local rates of relative sea-level rise, wave height, tide range, geomorphology, coastal slope, and rate of shoreline change. Using this information, the BN is used to make probabilistic predictions of shoreline change in response to different future sea-level rise scenarios’. See same area of CA and look at the area of south San Francisco.

As you can see this new tool will help tremendously to manage areas and to get a broad idea of what is happening on the US coasts.

All for now-

Severe Weather Forecast in Southern States: Thousands with no Power and Heavy Rain in LA

This week we explore severe weather.

A very good source of information is the Weather Underground Severe Weather website (see current map below). 

In the southern states, Patricia's remnants left today thousands in Louisiana with no power and heavy rain. The threat of a few severe storms capable of producing damaging wind gusts or isolated tornadoes will continue along the Gulf Coast into Monday. Patricia's mid- and upper-level energy helped spawn a non-tropical surface low pressure system in the Gulf of Mexico. That low will make the environment at least marginally favorable for rotating thunderstorms that could spawn brief tornadoes through Monday.

Heavy rain will continue to stream into Louisiana and neighboring southwestern Mississippi on Sunday, threatening to trigger major flooding.

In addition to the flooding rain, southern Louisiana will remain at risk for isolated tornadoes as occasional gale-force winds will create rough seas over the western Gulf of Mexico to end the weekend.

A tornado was confirmed by NWS Storm Survey Sunday afternoon in Destrehan, Louisiana, just outside of New Orleans. One woman was injured due to damage to her mobile home according to local emergency management.

Also, the risk of flash flooding will affect far more people over the next couple of days.

http://www.wunderground.com/severe.asp

http://www.weather.com/news/news/southern-plains-flood-threat-texas-6-things-to-know

http://www.accuweather.com/en/weather-news/live-blog-flooding-corsicana-houston-texas-oklahoma-louisiana-arkansas-patricia/53160429

LANDSLIDES & ENSO

Wildfires potentially increase the risk of landslides.

This is not new in the Western US. The USGS Landslide Hazards Program alerts of the danger of landslides after a rainstorm in areas of recent wildfires, explaining what to do before and during an event. This makes me think of a very probable strong El Niño event this year after all the wildfires the state has endured so far…

NOAA just prepared an updated prediction that can be seen here. Basically, they say as today El Niño conditions are present and that there is an approximately 95% chance that El Niño will continue through Northern Hemisphere winter 2015-16, gradually weakening through spring 2016.

El Niño and La Niña, together called the El Niño Southern Oscillation (ENSO), are periodic departures from expected sea surface temperatures (SSTs) in the equatorial Pacific Ocean. These warmer or cooler than normal ocean temperatures can affect weather patterns around the world by influencing high and low pressure systems, winds, and precipitation

Another good source of information is the California Geological Survey (CGS), which has produced numerous maps that show landslide features and delineate potential slope-stability problem areas.

FEMA always is also a good place to keep informed about these hazards and what to do before, during, and after.

Maps of risk areas can be downloaded and studied (regional and local examples here), which would help the managers and planners know which areas will be needing help first/more frequently.

10/17/15 UPDATE:
Flash floods sent water flowing into South CA roads.  All lanes of California's Interstate 5 reopened Friday evening after a massive mudslide pushed up to five feet of mud across the roadway Thursday, trapping cars and forcing crews to close the highway in both directions for nearly 40 miles. 

Meanwhile, State Route 58 is expected to remain closed for days after the same storm system caused flash flooding and dangerous mud flows, trapping about 200 cars there in mud as deep as 6 feet.

More information at links below:

http://www.conservation.ca.gov/cgs/information/publications/ms/documents/ms58.pdf

http://landslides.usgs.gov/hazards/

http://www.conservation.ca.gov/cgs/geologic_hazards/landslides/Pages/Index.aspx

http://www.ready.gov/landslides-debris-flow

http://www.cjpia.org/news/news-and-updates/news-and-updates/2015/10/05/strong-el-ni%C3%B1o-probable

http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

http://cdfdata.fire.ca.gov/incidents/incidents_current
http://www.weather.com/news/news/california-flooding-mudslides-stranded-motorists

http://www.nytimes.com/2015/10/17/us/a-wall-of-mud-in-california-and-warnings-to-heed-el-nino.html?hp&action=click&pgtype=Homepage&module=second-column-region&region=top-news&WT.nav=top-news