Arizona Geology Blog

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blog of the State Geologist of ArizonaLee Allison
Updated: 10 min 23 sec ago

Aftershock felt in Duncan area

Sun, 2014-11-23 16:37
Local residents reported feeling an aftershock to the Duncan earthquake on at 7:38 a.m. on Friday, Nov. 21.    The USGS posted the location for the event today, with a magnitude of 2.8.  This is the first aftershock felt in the area for many weeks.  The M=5.3 Duncan earthquake hit the eastern Arizona locale on June 28.   [Right, orange star marks aftershock epicenter.  Credit, USGS]

AZGS has posted an article online describing the main shock and our deployment of a temporary portable seismic array to locate and measure the hundreds of aftershocks -
Categories: AZGS Web Posts

How did we miss this story about vampires in abandoned mines in Arizona?

Sat, 2014-11-22 10:21

Well, Arizona, it looks like we had a chance to rid Arizona of vampires in our abandoned mines, but we blew it.   
Joe Hart won re-election as State Mine Inspector  a couple weeks back with over 1 million votes or 98.29% of the votes cast.   There was no organized opposition, but write-in votes totaled 18,312.  The Secretary of State's office has not posted who got those write-ins but I wonder if some of them didn't go to write-in candidate Ian Kobe who ran on a campaign of "No Arizona Mine Draculas."
His Facebook site (his only campaign outlet?) says "A vote for Ian Kobe is a vote for an AZ with less Draculas!" [sic] and laments that children cannot play in abandoned copper mines because Joe Hart has not cleaned out the vampire dens.
I know and work with Joe. I interviewed him on our video magazine "Arizona Mining Review" and I have to admit, never once has he mentioned vampires, let alone vampires in mines, active or abandoned. Joe, all I can say is that I'm speechless!

And the Arizona news media, obviously beholden to the pro-vampire community, ignored this burning issue in the Mine Inspector's race.  I had to read the Chicago Sun Times to find out about it.   


And all this raises the question that if the mines are full of vampires, can zombies be far behind?
So kids, you're going to have to stay out of those old mines for a while longer.

Categories: AZGS Web Posts

Grand Canyon North Rim quake

Fri, 2014-11-21 16:40
A magnitude 2.9 earthquake occurred  shortly after noon today on the north side of Grand Canyon.  The USGS placed the epicenter about 19 miles northwest of Grand Canyon Village, but Dr. Jeri Young who runs the Arizona Broadband Seismic Network here at AZGS, places it further northeast. [Right, red star marks USGS epicenter.   The red circle marked "112114" marks the AZGS location]

Jeri used 3 of Northern Arizona University's nearby analog seismic stations and a different crustal velocity model than the USGS model.     However, they  used 42 phases and we used only 9 in making the calculation, so we are not sure which is the more accurate location.
Categories: AZGS Web Posts

Investors keep sand operation running on Navajo Reservation

Wed, 2014-11-19 21:04
Preferred Sands is one of the largest providers of sand for oil and gas production in the country, and their Arizona plant has the company's largest reserves.   According to a story in Reuters,  "privately held Preferred Sands produces and distributes frac sand and proppant materials used predominately in oil and gas shale drilling. Its network of mines have the capacity to produce more than 9 billion pounds of sand every year."

 Private equity firm KKR & Co LP invested $680 million in the company to shore up its operations.  
Moody's Investors Service said "the company's woes to competition in the frac sand industry, its lack of high-quality sand reserves, and a less developed logistical network relative to its major rivals."

Preferred Sands of Arizona says it has a total reserve size of 130 million tons of coarse sand.   The Arizona mine is located 150 miles west of Albuquerque, New Mexico on the Navajo Reservation. The plant is capable of producing approximately 2 million tons per year.

Categories: AZGS Web Posts

Resolution Copper shaft is deepest in North America

Wed, 2014-11-19 20:22

Shaft #10 at the Resolution Copper mine in Superior reached its final depth of 6,943 feet (2,116 m). The 28-foot diameter shaft is the deepest single lift shaft in North America, according to the company. [Right top, bottom of shaft #10.  Photo credit, Resolution Copper]

The Resolution mine would produce an estimated 25% of the nation's copper for the next 40 years once it's completed.  [Right bottom, headframe for shaft #10. Photo credit, Nyal Niemuth]

"The completion of this 1.3 mile deep vertical shaft is truly unprecedented in North America,”
said Tom Goodell, General Manager of Shaft Development for the Resolution project. “The safe completion of the project represents a great engineering achievement, and I am particularly proud of the team -- made up mostly of miners from this area -- who made it happen.”

Development of the underground is dependent on a land exchange that needs Congressional approval.

[updated 11-20-14 with top photo]

Categories: AZGS Web Posts

Online resources for next year's Tucson gem-mineral-fossil showcase

Tue, 2014-11-11 18:47

The folks at Visit Tucson provided updates about the next Tucson Gem, Mineral & Fossil Showcase, which runs  January 31-February 15, 2015. [photo credit Visit Tucson] Here is the latest news:
  • A new wholesale show will move into the Grand Luxe Hotel & Resort, formerly the Grant Inn, at Grant & I-10
  • The Whole Bead Show is now a trunk show located at Homewood Suites by Hilton Tucson/St. Philip's Plaza University on River Road.
  • Tucson Bead Show has relocated to Radisson Suites Tucson on Speedway for 2015.
  • The Holidome show is moving to its own tent and property just west of the Holiday Inn Hotel & Suites Tucson Airport-North.
They regularly update information on each of these, as well as the 36 other shows, at

The theme for the 2015 Tucson Gem & Mineral Show® is Minerals of Western Europe. Check out the show details using their brand new website at and the Visit Tucson show site at

Tips for staying up to date:
  • Follow them on Twitter (@TucsonGems) and Pinterest (TucsonGems)
  • Visit the website as well as the mobile site at
And during the Showcase:
  • Call Gem Show Hotline at 520-622-GEMS! Staffed 24/7, a joint initiative of Visit Tucson and Tucson Fire Department (Hotline is open January 20-February 15, 2015.)
  • There will be welcome tables at Tucson International Airport (baggage claim areas), running January 28-February 8, 2015 and at Tucson Convention Center during the American Gem Trade Association Show (AGTA) and the Tucson Gem & Mineral Show® (TGMS)
  • Tucson Visitor Center in La Placita Village has all the latest information on Downtown restaurant openings, local attractions and directions. Open Mon.-Fri., 9 a.m.-5 p.m. and Sat.-Sun., 9 a.m.-4 p.m.
  • Stop and chat with one of the City of Tucson’s volunteer docents. You will find them peppered throughout the Downtown area wearing logo’d shirts and ID badges, so you know they are official. They will have the tools necessary to point you in the right direction. This service runs January 30-February 15, 2015.
Thanks to Jane Roxbury and Laurie White at Visit Tucson for the updates.
Categories: AZGS Web Posts

Report on Duncan earthquake aftershocks

Sun, 2014-11-09 09:11

The first report on the magnitude 5.3 Duncan earthquake is posted on the Arizona Geology online magazine page at

The report author, Dr. Jeri Young, runs the Arizona Broadband Seismic Network at AZGS.  She continues to analyze the aftershocks and source mechanisms.    A summary of the article:

"A magnitude 5.3 earthquake occurred near Duncan, AZ at approximately 10 pm on June 28th, 2014. The earthquake shaking was strong and caused moderate damage in the Duncan area; it was felt throughout southeastern Arizona  and was recorded by seismometers around the globe. The earthquake began about 7 km (4.4 miles) below the surface, and we have found no evidence that the earthquake ruptured the earth’s surface. Fairly minor damage was reported in Duncan and Safford; cracks developed in concrete structures and at least one home foundation, several trailer homes were displaced, and glassware flew out of cupboards. This was the largest earthquake to occur in southeastern Arizona – southwestern New Mexico in 75 years, and it serves as a reminder that Arizona does indeed have earthquakes and earthquake hazards.
In the days immediately following the main shock, the Arizona Broadband Seismic Network (ABSN), operated by the AZGS, recorded 156 aftershocks in the M 1.6 to M 3.6 range; however, the locations of the smaller events are uncertain because they were not recorded by many seismic stations. Since June 28th, thirty aftershocks ranging from M 2.6 to M4.1 [right] have been reported by the U.S. Geological Survey; all of the earthquakes occurred at depths of approximately 5 to10 km (3 to 6 miles). The largest aftershock, an estimated M 4.1, occurred on July 11th. Some residents felt strong shaking while light damage was reported."

Categories: AZGS Web Posts

Construction update at US89 landslide

Thu, 2014-11-06 08:20

Heavy construction has been underway since this summer on building a giant buttress below the landslide that closed US highway 89 southwest of Page.    ADOT has a webpage with updates on the work, but also posts updates on their blog with the latest on September 3.

A couple of weeks ago they added an extensive set of photos of the construction work on   [Right, view from US89 of the  work on the landslide materials and the buttress.  Credit, ADOT]

The construction is expected to cost in the area of $35 million. Another ~$20 million was spent to upgrade and pave route Navajo 20 as a temporary bypass around the slide to maintain access to Page.   There are no estimates of the economic losses due to the lengthy detours and semis getting stuck in soft sand, or to the loss of business in Page.

Categories: AZGS Web Posts

M2.0 earthquake near Fredonia

Thu, 2014-11-06 08:04
There was a magnitude 2.0 earthquake at 10:15 p.m. local time last night, about 9 miles ENE of Fredonia.  [Right, orange star marks the epicenter. Credit, USGS]
Categories: AZGS Web Posts

Drought is causing regional uplift, provides estimates of water loss

Sat, 2014-11-01 15:12

Drought in the western U.S. has caused loss of water from the near-surface rocks that the crust is lighter and rising, according to a recent study published in the journal Science.  Based on the amount of uplift, they calculate the loss of 240 gigatons of water, equal to layer of water across the region 10-cm thick.   [Right, drought monitor, August, 2014. Courtesy of ADWR]

The abstract for the article is available online ( western United States has been experiencing severe drought since 2013. The solid earth response to the accompanying loss of surface and near-surface water mass should be a broad region of uplift. We use seasonally adjusted time series from continuously operating global positioning system stations to measure this uplift, which we invert to estimate mass loss. The median uplift is 5 millimeters (mm), with values up to 15 mm in California’s mountains. The associated pattern of mass loss, ranging up to 50 centimeters (cm) of water equivalent, is consistent with observed decreases in precipitation and streamflow. We estimate the total deficit to be ~240 gigatons, equivalent to a 10-cm layer of water over the entire region, or the annual mass loss from the Greenland Ice Sheet.But another study, by Don Argus at Jet Propulsion Lab and his colleagues, used the same algorithm as the Borsa et al team, found less uplift
and thus less water loss:
"California’s mountains subside up to 12 mm in the fall and winter due to the load of snow and rain and then rise an identical amount in the spring and summer when the snow melts, the rain runs off, and soil moisture evaporates."

"The seasonal surface water thickness change is 0.6 m in the Sierra Nevada, Klamath, and southern Cascade Mountains and decreases sharply to about 0.1 m east into the Great Basin and west toward the Pacific coast" References:

Adrian Antal Borsa, Duncan Carr Agnew, Daniel R. Cayan, 2014, "Ongoing drought-induced uplift in the western United States," Vol. 345 no. 6204 pp. 1587-1590
DOI: 10.1126/science.1260279

Argus, D. F., Y. Fu, and F. W. Landerer, (2014), Seasonal variation in total water storage in California inferred from GPS observations of vertical land motion, Geophys. Res. Lett., 41, 1971–1980, doi:10.1002/2014GL059570.

Thanks to Brian Conway at AZ Dept. of Water Resources for pointing me to the Argus et al, paper.
Categories: AZGS Web Posts

Talking with USGS geologist Floyd Gray about the Patagonia orange sludge

Sat, 2014-11-01 14:16

USGS geologist Floyd Gray [right, credit USGS] is my guest on the latest episode of "Arizona Mining Review," our online video magazine, that was broadcast on Wednesday, October 29.  Floyd described the "orange sludge" recently found in a drainage in the  Patagonia area in southern Arizona, and its relation to historical mining activities.
As usual, the show was recorded and posted to our YouTube channel.   The direct link to the show is at The interview with Floyd begins about half way into the 30-minute show.
One of our professional geologist viewers shared the following comments:
" the "environmental" half of my career I had the opportunity to study high-iron orange sludge associated with both closed mines and (active & inactive) landfills in many locations and many rock-chemistry environments.  In every case the causative mechanism is the same: low pH and Eh ground water puts ferrous iron into solution, and when that water comes into contact with more neutral, high oxygen (high Eh), the precipitation occurs virtually instantly as the iron goes to ferric.

I was impressed with Dr. Gray and his approach to the issue (which is same as mine; you must understand the causative mechanism or you will have not a prayer of undertaking a corrective action that will work).

One point I wish he had mentioned.  In the presence of ferric iron, the solubility of lead is a very low number, approaching the reciprocal of Avogrado's Number (i.e., one to one hundred atoms of lead per mole of water)."

The AZGS YouTube channel is at
All previous episodes of AMR are available at:
Categories: AZGS Web Posts

AZGS geologists will lead field trip to Sabino Canyon debris flows

Sun, 2014-10-26 09:28

AZGS geologists Dr. Phil Pearthree and Dr. Ann Youberg will lead the Arizona Geological Society Fall Field Trip - "Debris Flows Shape the Sabino Canyon Landscape - look out below!"Sabino Canyon Visitor Center Patio, located at 5900 North Sabino Canyon Road, Catalina Foothills, Arizona.
Date: 15 Nov 2014 8:30 AM UTC-07:00 Debris Flows Shape the Sabino Canyon Landscape - look out below!

Field Trip Leaders: 
Ann Youberg and Phil Pearthree, Arizona Geological Survey - Environmental Geology Section

Tour Description: AGS Members and their guests are invited to join the Arizona Geological Survey tour of debris flows in Sabino Canyon.

During late July 2006, heavy rainfall in southern Arizona produced record flooding in several larger drainages and triggered numerous debris flows in the Santa Catalina Mountains and elsewhere throughout southeastern Arizona mountain ranges.  These debris flows did a remarkable amount of geomorphic work in a very short time, eroding hillslopes and channels and transporting very coarse sediments that garden-variety 100-year floods likely will not move.

Field Trip Date/Time/Location: Saturday, November 15, 2014.
Check-in begins at about 8:30 AM at the Sabino Canyon Visitor Center Patio, located at 5900 North Sabino Canyon Road, Catalina Foothills, Arizona.

Route: We will catch the 9:00 A.M tram and take it to Rattlesnake Wash.  Here and elsewhere along the tram road, we will examine debris flow deposits that formed in 2006.  The final stops will be at the top or northeast end of the tram road, elevation approximately 3,200 feet.  We return to the Sabino Canyon Visitor Center via the tram or down the Telephone Line Trail, about a 3-mile walk. The field trip will end around 12:30 PM.

Conditions & Recommendations:  All attendees should wear appropriate footwear for moderate hiking, which will be mostly along the tram road. Long pant and long-sleeve shirts are recommended for protection from the sun and vegetation. Be sure to bring your own snacks and water, as none will be provided by the AGS.

Guidebook:  Field trip guidebooks will be provided to trip participants.  One copy is recommended to be shared among couples or family members. 
The guidebook will summarize the mechanisms responsible for triggering debris flows, the damage they can do, how frequently they may occur, and the importance of these extreme events in shaping the mountain landscapes of Arizona.

Additional guidebooks will be produced by the AGS following the trip, which can be purchased at our dinner meetings.
Fees:  This field trip will be free to all AGS members and guests.   However, each participant will be responsible for a $5.00 parking fee at the Sabino Canyon Visitor Center and an $8.00 tram ticket for the ride up the mountain.Contact: AGS VP Field Trips Ralph Stegen at or (520) 498-6811 with any additional questions.

More information and online registration:  Fall Field Trip - Debris Flows Shape the Sabino Canyon Landscape - look out below! 

Categories: AZGS Web Posts

Earth and Space Exploration Day at ASU this Saturday

Thu, 2014-10-23 17:32
ASU hosting Earth and Space Exploration DaySaturday, October 25, 2014 (9 a.m. - 3 p.m.) LOCATION: Interdisciplinary Science and Technology Building IV (ISTB 4), Arizona State University, Tempe
Earth and Space Exploration day is a free annual fall event hosted by the School of Earth and Space Exploration (SESE) on ASU’s Tempe campus inside/outside ISTB 4. The SESE community offers special science-related activities from 9 a.m. - 3 p.m. for students age five and up, families, educators and anyone interested in exploring Earth and space. One of the biggest attractions is ISTB 4 with its Gallery of Scientific Exploration offering a variety of interactive exhibits and the Marston Exploration Theater, which will be running 3-D astronomy shows. Visitors can also see a replica of Curiosity Mars rover, explore "A" Mountain (Tempe Butte) on a guided field trip, bring rock samples for Dr. Rock to examine, and so much more!

SESE’s research portfolio includes projects on every continent of the world, and extends to the Moon, Mars, Mercury, and beyond. We are taking photos of the lunar surface with special cameras, sampling the Red Planet using robotic rovers, studying earthquakes big and small, investigating mud volcanoes in Indonesia and much, much more! Each year, the SESE community brings to life its research through innovative hands-on activities as part of this special Earth and Space Exploration Day.

Attending Earth & Space Exploration Day 2014 is free (including parking). But you can help us anticipate the number of people that will attend by pre-registering at Pre-registration also allows a speedy check-in for you and your family.

The Marston Exploration Theater will be offering 3-D astronomy shows.
The Center for Meteorite Studies features interactive displays, touchable specimens, and a video display of the collection’s specimens. Staff will be on hand to inspect potential meteorite specimens in person. Only one sample will be identified per person.

The Lunar Reconnaissance Orbiter Camera (LROC) Science Operations Center, located in Interdisciplinary A, will be open. Visit the Moon rock and enjoy a guided walk through of the Visitors Gallery.

[taken from the ASU SESE site]
Categories: AZGS Web Posts

Arizonans to drop, cover, and hold on during the Great Shakeout

Wed, 2014-10-15 20:52

Thursday is ShakeOut Thursday. At 10:16 am on 10/16, 120,000 Arizonans and 24 million people worldwide will “Drop, cover and hold on” to practice responding to earthquakes.  The  organizers remind us that everyone, everywhere, should know how to protect themselves in an earthquake. Even if earthquakes are rare where you live, they may happen where you or your family travel.

Great ShakeOut Earthquake Drills are an annual opportunity for people in homes, schools, and organizations to practice what to do during earthquakes, and to improve preparedness.

I've lost track of the number of people who say that Arizona doesn't have earthquakes. Not true.  The recent magnitude 5.2 Duncan earthquake with hundreds of aftershocks reminded eastern Arizonans of the risk.  Learn more at

Categories: AZGS Web Posts

National Fossil Day - Arizona's state fossil is petrified wood

Wed, 2014-10-15 19:46

Happy National Fossil Day!   The National Park Service organizes the events and promotional materials -
The Arizona State Fossil, petrified wood, is among a long list of state symbols shown on the Arizona Secretary of State's website.

Categories: AZGS Web Posts

AZGS hazard viewer added to Arizona Emergency Information Network

Mon, 2014-10-13 20:00
The AZGS online hazards viewer is now linked in throught the Arizona Emergency Information Network -

The viewer currently inlcudes information on earth fissures, active faults, earthquake epicenters, flood potential, and wildfire risk.

Categories: AZGS Web Posts

Geologic data program preserves mining files in Arizona

Mon, 2014-10-13 08:19
Congress is considering reauthorization of the National Geological & Geophysical Data Preservation Program, first passed in 2005.    The program, based in the USGS, puts up small matching funds to help state geological surveys to catalog and digitize our vast archives.    Since 2011, AZGS has successfully competed for funds to help digitize the files we acquired in the merger of the Arizona Dept. of Mines & Mineral Resources.    These files are being placed online at for free downloading.   We are working through hundreds of thousands of pages of files and reports, 10,000 maps, and thousands of historical photos, to get them scanned, catalogued, georeferenced and online.

Randy Showstack, reporter for AGU's Eos newspaper, covered the hearing in the House last month, and wrote a story describing the scope of the program nationally and some of its other impacts -

AZGS funding from the program has ranged from about $25 to $40 thousand per year, among the larger grants in the country.   Over, Congress has appropriated about $8 million since 2007, with $4.6 million going to state surveys.
Categories: AZGS Web Posts

New role with National Data Repositories

Sat, 2014-10-11 19:02

Since the recession hit, the Arizona Geological Survey has relied on external grants to replace state appropriations so that 80-90% of our budget now comes these sources. Fortunately, our expertise in open data and data integration has put us in a national leadership role and increasingly a player in the international data environment, to compete for funding.
I'm back from Baku, Azerbaijan and the meeting of the National Data Repositories consortium, where I was chosen as Chair of the 30-nation organization for the next 18 months.  
The meeting organizer, Energistics, is releasing the following statement regarding the meeting:

Managing growing volumes of data generated by the oil and gas industry is a common challenge for all oil regulators around the world. Typically regulators have resolved the problem by establishing National Data Repositories (NDRs). The twelfth meeting of these oil regulators to discuss common issues and problems was held in early October 2014 in Baku, Azerbaijan. The event was hosted by the State Oil Company of Azerbaijan Republic (SOCAR) and it was appropriate that the conference was held in view of the first commercially drilled oil well in the world. [Right, me standing at the world's first commercial oil well, drilled in 1847]
Regulators from 22 countries plus delegates from major oil industry service companies and software suppliers met to share best practices and update the progress made on collaborative projects since the last meeting. More importantly, they discussed how to improve the quality of data delivered to regulators, how to improve the profile of NDRs and how to enhance the value of the data.  Data management best practices increase efficiency, leverage new technology developments and improves industry compliance while promoting economic development and protecting the environment.
Tirza van Daalen, TNO – Netherlands, and Chair of the meeting said, “This was an excellent meeting that exceeded our expectations. There is a real desire for regulators to cooperate and we are expecting real progress in various data standards areas before the next meeting in North America in 2016”.
Jerry Hubbard, President & CEO of Energistics, organizers of the event said, “I believe the next eighteen months will show real progress in collaboration between regulators as they assimilate the lessons learned and the benefits of sharing."
Two of my goals as Chair are to expand on interactions and collaborations among the data repositories between meetings, and to get more of the many U.S. state and federal oil gas regulatory agencies participating in NDR in advance of the Spring 2016 conference to be held in North America.  The U.S. oil and gas community has a lot to learn from and to share with our international counterparts.
I was excited to find that the work AZGS is doing with the US Geoscience Information Network (USGIN) appears to map easily to a quickly growing area of data "business rules." Delegates to the meeting suggested that the 1,000+ data parameters we developed in 30 data content models might form the basis for a global framework.
For more information on the National Data Repository Work Group and NDR2014, please visit   Find out more about USGIN at

Categories: AZGS Web Posts

Geosciences is top UA program in Performance Ranking of Scientific Papers for World Universities

Sat, 2014-10-11 18:11

The University of Arizona scored high in the 2014 Performance Ranking of Scientific Papers for World Universities, with the Geosciences Department achieving the highest ranking of any program in the university.
The notice to the University of Arizona said it "ranks 73 in Overall Ranking, 6 of its fields are enrolled in top 300 Ranking, and 10 of its subjects are enrolled in top 300 ranking. Overall, 17 of its respective rankings have entered The 2014 Performance Ranking of Scientific Papers for World Universities."
  *   73 for Overall Ranking  *   20 for Geosciences  *   21 for Physics  *   23 for Environment/Ecology  *   33 for Agriculture
According to NTU, "The 2014 Performance Ranking of Scientific Papers for World Universitie is released by the National Taiwan University Ranking (NTU Ranking). Formerly known as the HEEACT Ranking during 2007-2010, this ranking program offers annual performance rankings for world universities based on the production and impact of their scientific papers.
The Performance Ranking of Scientific Papers for World Universities is a stable and reliable ranking for universities devoted to scientific research. It is entirely based on statistics of scientific papers which reflect three major performance criteria—research productivity, research impact, and research excellence. This year, in addition to the overall performance ranking, we also offer 6 field-based rankings and 14 subject-based rankings. We are committed to continually update and release new annual overall, field, and subject rankings in the future. For more information about our ranking program, please go to"

Categories: AZGS Web Posts

Updated subsidence maps released with standardized legends

Sat, 2014-10-11 11:13
Arizona Dept. of Water Resources has updated all the land subsidence maps on ADWR’s website so that they are all using the same color scale.  Project manager Brian Conway expects this will help eliminate any confusion that people are having when comparing maps for one or more area and when looking at different periods of time.  There are 213 land subsidence maps available for download as pdfs.  [Right, interactive subsidence map viewer.  Yellow boxes outline basins with maps available. ADWR]

He has also added land subsidence rate maps for each land subsidence feature and there are a total of 45 land subsidence rate maps available for download.  The land subsidence rate maps also use a same color interval.
Categories: AZGS Web Posts