Volcano monitoring: The legacy of the 1975 earthquake: 50 years of study on the southern flank of Kilauea

The 1975 Kalapana earthquake brought about major changes in the lives of people affected by deaths and damage, as well as major changes in our understanding of Kilauea's southern flank.

Scientists at the USGS Hawaiian Volcano Observatory have been collecting data and forming a hypothesis that Kilauea's southern flank could produce a large earthquake soon. The 1975 earthquake occurred on November 29, while their findings were awaiting print.

Previous large earthquakes, such as the 7.9 magnitude Great Kau earthquake of 1868, have been attributed to a nearly horizontal fault (décollement) at the boundary between the original oceanic crust and erupting lava from Mauna Loa and Kilauea. It is deepest below the middle of Hawaii Island and becomes slightly shallower towards shore.

Seismic and deformation data for the Kalapana earthquake indicated that initial movements were also on the fault fault, but the 1975 rupture was more complex. Vertical displacements have also been observed along the top of several cliffs on Kilauea's south side. This pali is the surface expression of the Helena fault system. This indicates that both the Helena Fault System and the Helena Detachment Fault slipped during the 1975 earthquake, leading scientists to wonder whether the Helena Fault System might connect directly to the Helena Detachment Fault.

Additional data collection in the past 50 years has shown that this scenario is not the case. One key piece of evidence is from a series of marine seismic reflection profiles published in 2000 – a technique that captures images inside the crust, similar to an MRI.

Reflection profiles showed that the head bends in the Helena Fault System bend deeply and do not continue deep enough to intersect the thoracic region. This means that the Helena Fault blocks are smaller than they would be if they were connected to the separation layer and that the two structures are not directly connected.

After the 1975 earthquake, there was greater emphasis on monitoring the movement of the south side. The HVO and the University of Hawaii at Manoa installed continuous GPS instruments on the south side of Kilauea that recorded the constant seaward motion of the south side at a rate of about 5 cm (2 in) per year. They also showed that wing motion was not always constant. Every 2-3 years, the wing accelerates for 2-3 days, in a phenomenon called a slow glide event. These events released fault stress energy equivalent to a magnitude 6 earthquake, but they did so too slowly to generate any harmful vibrations.

Slow slip events have been observed on faults around the world, including the San Andreas Fault and the Cascadian Subduction Zone. Observing slow-slip events at Kilauea was key to showing that their occurrence is not limited to plate boundaries, but is a fundamental consequence of velocity-enhancing fault friction that can occur wherever such frictional conditions exist.

The 2018 magnitude 6.9 earthquake provided further insights into the 1975 quake. There was no evidence of movement on the Balice during this most recent earthquake. Given what we've learned about the structure of the South Side in the past 50 years, that's likely because the 2018 quake was smaller than the 1975 quake. Strong shaking during the 1975 quake may have been what set the Helena fault system in motion, a process called dynamic stimulation.

However, even in the event of a large earthquake, there is a limit to how far the Helena Fault Zone can move. Seismic reflection files published in 2000 showed that the fault fault creates an area of ​​raised crust (“toe”) as it approaches the surface. This finger acts as a brace on the flank, preventing large movements.

Our improved understanding of how Kilauea's southern flank behaves is part of the legacy of the 1975 earthquake, as is our appreciation of the magnitudes of earthquakes that can be generated at the fault line. Being well prepared for earthquakes is always a good idea. Information on how to prepare your home and family for earthquakes can be found at https://www.ready.gov/earthquakes.

Volcano activity updates

Kilauea Volcano has been episodic erupting within the summit caldera since December 23, 2024. The USGS volcano alert level is WATCH.

Episode 37 of the 9-hour lava fountain took place on November 25. The peak bulges again and the glow can be seen throughout the night from the southern vent. Another spring episode is likely, but at least a week later according to forecast models. No unusual activity has been observed along the East Rift Zone or the Southwest Rift Zone on Kilauea.

Mauna Loa does not erupt. Its USGS volcano alert level is at normal.

Three earthquakes felt in the Hawaiian Islands have been reported over the past week: an M3.4 earthquake 25 km (15 mi) east of Haleola at a depth of 4 km (2 mi) on November 26 at 4:24 a.m. GMT, a M4.6 earthquake 15 km (9 mi) southeast of Fern Forest at a depth of 5 km (3 mi) on November 25 at 11:49 p.m. GMT, and an M3.2 earthquake. 15 km (9 mi) east-east of Waikoloa at a depth of 30 km (18 mi) on November 20 at 3:43 p.m. GMT.

The HVO continues to monitor Kilauea and Mauna Loa closely.

Please visit the HVO website for previous Volcano Watch articles, Kilauea and Mauna Loa updates, volcano photos, maps, recent earthquake information, and more. Email questions to [email protected].

What Are The Main Benefits Of Comparing Car Insurance Quotes Online

LOS ANGELES, CA / ACCESSWIRE / June 24, 2020, / Compare-autoinsurance.Org has launched a new blog post that presents the main benefits of comparing multiple car insurance quotes. For more info and free online quotes, please visit https://compare-autoinsurance.Org/the-advantages-of-comparing-prices-with-car-insurance-quotes-online/ The modern society has numerous technological advantages. One important advantage is the speed at which information is sent and received. With the help of the internet, the shopping habits of many persons have drastically changed. The car insurance industry hasn't remained untouched by these changes. On the internet, drivers can compare insurance prices and find out which sellers have the best offers. View photos The advantages of comparing online car insurance quotes are the following: Online quotes can be obtained from anywhere and at any time. Unlike physical insurance agencies, websites don't have a specific schedule and they are available at any time. Drivers that have busy working schedules, can compare quotes from anywhere and at any time, even at midnight. Multiple choices. Almost all insurance providers, no matter if they are well-known brands or just local insurers, have an online presence. Online quotes will allow policyholders the chance to discover multiple insurance companies and check their prices. Drivers are no longer required to get quotes from just a few known insurance companies. Also, local and regional insurers can provide lower insurance rates for the same services. Accurate insurance estimates. Online quotes can only be accurate if the customers provide accurate and real info about their car models and driving history. Lying about past driving incidents can make the price estimates to be lower, but when dealing with an insurance company lying to them is useless. Usually, insurance companies will do research about a potential customer before granting him coverage. Online quotes can be sorted easily. Although drivers are recommended to not choose a policy just based on its price, drivers can easily sort quotes by insurance price. Using brokerage websites will allow drivers to get quotes from multiple insurers, thus making the comparison faster and easier. For additional info, money-saving tips, and free car insurance quotes, visit https://compare-autoinsurance.Org/ Compare-autoinsurance.Org is an online provider of life, home, health, and auto insurance quotes. This website is unique because it does not simply stick to one kind of insurance provider, but brings the clients the best deals from many different online insurance carriers. In this way, clients have access to offers from multiple carriers all in one place: this website. On this site, customers have access to quotes for insurance plans from various agencies, such as local or nationwide agencies, brand names insurance companies, etc. "Online quotes can easily help drivers obtain better car insurance deals. All they have to do is to complete an online form with accurate and real info, then compare prices", said Russell Rabichev, Marketing Director of Internet Marketing Company. CONTACT: Company Name: Internet Marketing CompanyPerson for contact Name: Gurgu CPhone Number: (818) 359-3898Email: [email protected]: https://compare-autoinsurance.Org/ SOURCE: Compare-autoinsurance.Org View source version on accesswire.Com:https://www.Accesswire.Com/595055/What-Are-The-Main-Benefits-Of-Comparing-Car-Insurance-Quotes-Online View photos