5 Critical Facts About The Recent Earthquake Swarms In Highland, CA That Every Resident Must Know

Highland, California, sits on one of the most seismically active regions in the United States, a reality underscored by a recent swarm of low-to-moderate magnitude earthquakes that have been recorded in the area as of December 2025. While most residents barely feel these smaller tremors—with recent activity including quakes in the M1.4 to M2.7 range—their frequency serves as a critical, ongoing reminder of the city's direct proximity to the notorious San Andreas Fault system. The latest data shows the Southern California region, including the San Bernardino Valley, experiences over a hundred small quakes each week, making preparedness not just a recommendation, but a mandatory aspect of life in this part of the Inland Empire. This constant seismic activity is a direct result of the colossal tectonic struggle between the Pacific Plate and the North American Plate, a geologic battleground that runs right through San Bernardino County. Understanding the specific fault lines and the local emergency response framework is the single most important action a Highland resident can take right now to mitigate risk and ensure safety when the inevitable "Big One" strikes.

1. Highland Sits Directly on the San Andreas Fault System

The most critical fact for any Highland resident is the city's intimate and perilous relationship with the San Andreas Fault (SAF). This is not a distant threat; the fault line runs so close that it is visible in parts of Highland's natural parkland.

The San Bernardino Fault Segment and San Jacinto Zone

The section of the SAF that runs through the region is known as the San Bernardino Fault segment. This segment is considered one of the most dangerous, as it has accumulated significant seismic strain over the centuries. Highland is also near the San Jacinto Fault Zone (SJFZ), a major strike-slip fault that runs parallel to the SAF and is often cited as the most active fault in Southern California. The interaction between these two major fault systems dramatically increases the overall seismic risk for the entire San Bernardino Valley.

The Cajon Pass Earthquake Gate Risk

Adding to this complex geological picture is the Cajon Pass, a critical transportation and infrastructure corridor located just northwest of Highland. Geologists refer to this area as an "earthquake gate" because it is a key junction where the San Andreas and San Jacinto faults interact. A major rupture originating at the Cajon Pass could cause catastrophic damage to the region's lifelines, including gas lines, water mains, and major freeways like I-15 and I-215, making Highland's recovery efforts particularly challenging.

2. The Latest Quake Swarm Is a Constant Warning

While the media focuses on large, damaging quakes, the real story in Highland, CA, is the constant, low-level seismic activity that never stops. This is what seismologists call a "swarm" or a heightened period of smaller tremors.

Recent Magnitude Readings

In the last few months of 2024 and heading into 2025, the area has seen a steady stream of earthquakes. For instance, a 2.6 magnitude earthquake was recorded near Highland in late November 2025 (or 2024), followed by a 2.7 magnitude tremor just days later. These events, though minor, are a clear indicator that the fault systems are under constant stress and movement. The data shows that the region experiences over a hundred quakes each week, with the strongest recent quake (M3.6) felt across the wider area.

Why Small Quakes Matter

The frequency of small earthquakes is not a sign that pressure is being released, as many people mistakenly believe. Instead, they serve as a crucial reminder of the potential for a massive event, often referred to as the "Big One." The constant minor shaking can also stress existing infrastructure, making older buildings more vulnerable when a major rupture occurs. Therefore, residents must take these frequent tremors as a sign to update their emergency plans and supplies.

3. San Bernardino County OES Preparedness is Your Local Lifeline

For Highland residents, the most direct and actionable resource for earthquake preparedness comes from the San Bernardino County Office of Emergency Services (OES). They coordinate the county-wide response and provide specific resources to help local families and businesses.

Key OES Action Steps

The San Bernardino County OES emphasizes a four-part strategy: Mitigation, Preparedness, Response, and Recovery. The most critical steps for the *preparedness* phase include:

• Develop a Customized Emergency Plan: This plan must be specific to your family's needs, including meeting points, out-of-state contacts, and a plan for pets.
• Build an Emergency Supply Kit (Go-Bag): This kit should contain at least three days' worth of non-perishable food and water (one gallon per person, per day), a first-aid kit, copies of vital documents (insurance, ID), a battery-powered radio, and necessary medications.
• Secure Your Home: Anchor heavy furniture, bookshelves, and water heaters to wall studs to prevent them from falling and causing injury or blocking exits during the shaking.
• Practice 'Drop, Cover, and Hold On': This is the universal safety protocol. You must practice dropping to the floor, taking cover under a sturdy table or desk, and holding on until the shaking stops. The OES heavily promotes participation in the Great California ShakeOut drill every October.

4. The State-Wide Early Warning System is Essential

Highland residents have access to California's state-of-the-art Earthquake Warning California system, which can provide a few crucial seconds of warning before the most damaging seismic waves arrive. These few seconds can be the difference between life and death.

How to Get the Warning

The early warning system relies on a network of ground-motion sensors that detect the first, faster-moving P-waves (Primary waves) of a quake before the slower, more destructive S-waves (Secondary waves) arrive. Highland residents should use the following tools to receive alerts:

• MyShake App: This mobile application, available for iOS and Android, is designed to send an alert directly to your phone when an earthquake is detected.
• ShakeAlert®: This is the underlying technology used by the MyShake App and other platforms to issue the warning.
• Wireless Emergency Alerts (WEA): Similar to Amber Alerts, these alerts are sent to your mobile device via the cell network for larger, more significant earthquakes.

These alerts provide the necessary time to perform the Drop, Cover, and Hold On action, shut off gas lines if safe to do so, or pull over safely if driving.

5. Aftershocks and Utilities Are the Immediate Post-Quake Threat

Once the ground shaking stops, the danger is not over. The period immediately following a major earthquake is dominated by the threat of aftershocks and compromised utilities.

The Aftershock Danger

Aftershocks are smaller quakes that follow the main shock and can continue for days, weeks, or even months. They can be strong enough to collapse structures already damaged by the main earthquake. It is essential to remain vigilant and avoid re-entering damaged buildings until they have been inspected by a professional.

Utility and Fire Risk

Earthquakes frequently rupture gas lines and electrical wiring, leading to a high risk of fire. If you smell gas, turn off your main gas valve *only if* your utility company advises you to do so and you know how. Do not turn it back on yourself; wait for a professional. The San Bernardino County OES stresses that after a major quake, you should be prepared to be self-sufficient for at least 72 hours, as first responders will be overwhelmed and unable to reach all areas immediately. Your emergency water supply and Go-Bag will be your most valuable assets during this critical recovery period.

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