Why Have Seismologists Moved from Richter to Moment Magnitude for Measuring Earthquake Intensity?

The Richter scale, developed in 1935 by Charles F. Richter, was the first scale to measure the size of earthquakes. The scale is logarithmic, meaning that each whole number increase on the scale represents a tenfold increase in measured amplitude and approximately 31.6 times more energy release. The scale was specifically calibrated for Southern California and used a particular type of seismograph, so it was most accurate for medium-sized earthquakes (M3 to M7) within a certain distance from the seismograph.

However, as our understanding of earthquakes has grown and technology has improved, seismologists have identified limitations with the Richter scale:

  1. Regional Limitations: The Richter scale was based on California’s geology and the specific seismographs used at the time. It does not scale well for extremely large or small earthquakes, nor does it account for variations in the Earth’s crust in different regions of the world.
  2. Energy Release: The Richter scale does not accurately estimate the energy released by very large earthquakes. The scale saturates around M7, meaning that it does not distinguish well between the energy released by the largest earthquakes, which can differ significantly.
  3. Seismograph Limitations: The original scale was based on the recordings from a particular type of seismograph that is not used as widely today. Modern seismographs provide more detailed data, and the Richter scale does not take full advantage of this.

To address these limitations, the Moment Magnitude Scale (Mw) was introduced by Hank and Kanamori (1979). It is based on the seismic moment of an earthquake, which is a measure of the total energy released by the earthquake. The moment magnitude scale is now the most common scale for measuring the size of earthquakes for several reasons:

  1. Global Applicability: Moment magnitude is calculated based on the physical properties of the earthquake (such as the rigidity of the Earth’s crust, the area of the fault that slipped, and the amount of slip) and can be used globally without regional corrections.
  2. Accuracy for Large Earthquakes: The moment magnitude scale does not saturate like the Richter scale. It provides an accurate measure of the energy release for very large earthquakes (greater than M7), which is essential for understanding their potential impact.
  3. Consistency: The scale provides a more uniform and consistent measure of an earthquake’s size, which is useful for both historical comparisons and scientific research.
  4. Detailed Data Use: Modern seismographs record a full seismic wavefield. Moment magnitude takes advantage of this data to provide a more complete picture of an earthquake’s characteristics.

Because of these advantages, the moment magnitude scale has largely replaced the Richter scale for most seismological applications, especially for earthquakes that are recorded at long distances from the epicenter or that are very large.

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Why does Japan frequently experience earthquakes?

Japan, a country renowned for its rich cultural heritage and technological advancements, also faces a unique natural challenge: it is one of the most earthquake-prone regions in the world. The reason behind this frequent seismic activity is deeply rooted in the country’s geographical positioning.

Situated on the Pacific Ring of Fire

Japan is located atop the Pacific Ring of Fire, a zone teeming with tectonic activity. This region is where four major tectonic plates – the Pacific, North American, Eurasian, and Filipino – converge. These colossal rock formations serve as the unstable foundation upon which Japan rests. The constant shifting and colliding of these plates lead to frequent earthquakes, some of which have the potential to trigger devastating tsunamis, especially if the disturbances occur underwater.

Japan’s Ingenious Adaptation

In response to this volatile environment, Japan has become a world leader in earthquake preparedness and building resilience. Homes, hospitals, schools, and other critical infrastructure in Japan are constructed to endure the tremors, adhering to strict regulations regarding design and materials. Earthquake drills are a regular practice in schools and workplaces, reflecting the nation’s commitment to preparedness. While earthquakes are inherently unpredictable, Japan’s proactive stance on disaster readiness is commendable and consistent.

The Contrast: Japan vs. Other Earthquake-Prone Regions

A stark contrast to Japan’s preparedness was observed in last year’s tragedy in Turkey, where a 7.8 magnitude earthquake led to catastrophic destruction and loss of life. In comparison, Japan’s resilience was evident during a recent 7.6 magnitude earthquake, which resulted in minimal damage. This disparity highlights the effectiveness of Japan’s disaster readiness and building standards. However, challenges like tsunamis remain, posing significant threats that require continuous vigilance and innovation.

The Role of Early Warning Systems and Structural Health Monitoring

In light of Japan’s seismic vulnerability, the importance of earthquake early warning systems cannot be overstated. These systems provide crucial seconds to minutes of advance notice, enabling people to seek safety and shut down critical operations, thereby mitigating the impact.

Similarly, structural health monitoring is vital for assessing the integrity of buildings and infrastructure. Continuous monitoring can detect potential weaknesses or damages early, allowing for timely repairs and reinforcement, which is essential in earthquake-prone regions.

QuakeLogic: A Pioneer in Earthquake Preparedness

In the realm of earthquake early warning and structural health monitoring, QuakeLogic stands out with nearly two decades of experience. QuakeLogic’s expertise in these fields is not just about technology; it’s about saving lives, protecting properties, and enhancing resilience against nature’s fury.

As Japan continues to navigate its challenging geological landscape, the lessons learned and technologies developed there are invaluable to the rest of the world. QuakeLogic remains committed to contributing to this field, providing state-of-the-art solutions for disaster readiness and structural integrity.

Connect with us for more insights on earthquake preparedness and innovative solutions. Follow our journey as we continue to support earthquake-prone regions like Japan in their quest for safety and resilience.

AGING DAMS, CLIMATE CHANGE AND EARTHQUAKES – HOW CAN MONITORING HELP TO PREVENT DISASTERS?

  • 15 Jan 2024
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Devastating climate change, including killer heat waves and severe flooding, adversely affects the infrastructures our communities rely on. Dams in particular become increasingly more vulnerable to climate change due to aging. Rapidly rising water levels and frequent floods add extra stress to dams, reservoirs and waterways, pushing them to their design limits. A failure to upgrade dams in response to deterioration in structural health may result in a catastrophic impact on the people and environment.

The most recent examples are the failed Edenville and Sanford Dams in Midland, Michigan due to rapidly rising waters after days of heavy rain. The collapsed Edenville Dam, constructed in 1924, was rated in unsatisfactory condition in 2018, while the Sanford Dam, which was built in 1925, was given a fair condition rating by the State.

In 2017, major flooding from the damaged Oroville Dam in Northern California forced the evacuation of nearly 200,000 Californians. The Oroville Dam was completed in 1968, toward the end of the golden era of dam construction. This was a wakeup call for owners of aging dams across the country, as climate change continues to add stress to these structures.

California has additional challenges due to active earthquake faults, including the Hayward and San Andreas faults, which scientists predict are due for a large earthquake. Among the dams now considered to be at risk are the Anderson Dam and the Calaveras Dam, both close to fault lines in Silicon Valley. According to the NY Times, California’s most troubled large dam is at Lake Isabella. This dam was built on the Kern River near Bakersfield by the Army Corps of Engineers in the 1950’s on what was thought to be an inactive fault. However, this fault has been active since then.

Another major threat to dams is scouring. Numerous aging dams have experienced severe erosion of their unlined spillways. This erosion can lead to damage and even failure of dams and consequently can threaten public safety, properties, infrastructure and the wider local environment.

There are a number of unfortunate examples of dams failing due to earthquakes, flooding or scouring where early signs of deficiencies might have been detected if a proper structural health monitoring (SHM) system had been in place.

Introducing SMARTDAM

QuakeLogic is the only company using a cloud-based, AI-powered technology platform to perform continuous, autonomous assessments using data from sensors on the dam structure.

QuakeLogic’s Sensor data Management, Assessment and Repository Technology (SMART) platform transforms a dangerous, aging dam into a SMART dam able to alert officials to critical deterioration. It also significantly reduces needed search and inspection efforts following any seismic or other impact event such as settlement, scouring, etc.

The SMART platform integrates manually and digitally read sensor recordings into a fully automated unified monitoring system. It facilitates the acquisition and analysis of critical sensor data needed by the dam operators for proper operation and maintenance, and most importantly, for the safety assessment of the dam. It routinely collects, organizes and evaluates sensor data, and sends immediate notifications with ACTION PLANS upon exceedance of programmed thresholds, generating PDF reports regularly and on-demand.

The SMART platform is a cutting-edge system that works with various types of sensors such as accelerometers, tiltmeters, potentiometers, strain gauges, thermocouples, weather stations, piezometers and seepage monitors. Comprehensive analytic information is visible in real-time on the mobile-friendly dashboard, providing proof and PEACE OF MIND that a dam is performing as expected.

In addition to our SMART platform, our proprietary earthquake early warning (EEW) alerts provide a window of opportunity for action before earthquake shaking begins at the site. It can even trigger automated actions such as opening spillways, closing roads, etc. – when every second counts.

Easy-to-understand, engineering-quality information on the real-time health of the dam together with the ACTION PLAN support operators to make informed decisions. Whether planning maintenance activities, or prioritizing critical response actions, QuakeLogic has you covered.

QuakeLogic’s monitoring system instantly detects any issue that could impact the structural integrity of the dam, allowing corrective measures to be implemented and avoiding a potential future disaster.

For details, contact us at info@quakelogic.net