15.7: Detailed Figure and Video Descriptions

Figure 15.1.2

A map of California’s geomorphic provinces with the Peninsular Ranges province emphasized. The Peninsular Ranges province borders the Pacific Ocean and is south of the Transverse Ranges province and west of the Colorado Desert province.

Figure 15.1.4

Although the Elsinore and San Jacinto faults are not labeled in the figure, they are clearly visible in the topography as strikingly linear features that bound mountain ranges. West of the Elsinore fault are the Santa Ana Mountains, which are also the northernmost range, and the Laguna Mountains which are further south. The Elsinore-Temecula Valley and the Agua Tibia Mountains parallel the Elsinore fault. The Perris Plain sits between the two faults. The San Jacinto Mountains and the Santa Rosa Mountains, just to their southeast, are both east of the San Jacinto fault.

Figure 15.1.6

Simplified fault map of southern California which locates the San Andreas fault zone and the major fault zones in the Peninsular Ranges provinces. In order, moving west and away from the San Andreas fault zone, are the San Jacinto fault zone, the Elsinore fault zone and the Newport-Inglewood fault zone. The other labeled fault zones on the map are not part of the Peninsular Ranges and can be ignored for this discussion.

Figure 15.2.1

A possible reconstruction of the supercontinent of Rodinia starting to break apart at 1.1 Ga or 1100 Ma. Rodinia is equatorial and what will become Madagascar, India, East Antarctica, Australia, South China, and Siberia are in the northern hemisphere. Laurentia and Baltica straddle the equator, with Rio Plato, Amazonia, and West Africa extending from them into the southern hemisphere. Congo-Sao Francisco and Kalahari are larger islands to the south and west of the main landmass.

Fold mountain belts related to building Rodinia, or remains from a pre-Rodinia supercontinent, connect Madagascar, India, and Australia to East Antarctica; and also connect Laurentia to Rio Plato and Amazonia. The island of Congo-Sao Francisco is segmented by another, and the island of Kalahari has one on its northern border.

There is no fold mountain belt connecting East Antarctica and Laurentia and they are starting to separate and the area between becomes the proto-Pacific ocean basin.

Figure 15.2.4

This figure tries to capture 30 million years of tectonic history in southern California in a sequence of maps. The important relationships change with each successive map and therefore they are labeled by their timing expressed as millions of years ago, abbreviated as “Ma” on each map. What is important is how the tectonics change with time, and that is described in detail in the text.

To delineate the tectonic changes, the plates are labeled - Farallon, Juan de Fuca, Cocos, Pacific, and North American. There relative locations are described in the text. The types of plate boundaries are indicated by variations in line width, color, and the addition of “teeth” symbols and arrows as indicated in the legend. In the text, these are named and described without using the symbolism of the visual descriptors.  Triple junctions, where three plates meet, are also indicated by symbols and labels and their motion - moving apart through time is tracked be descriptions in the text. To help connect each map with the geology of today, some major cities and geomorphic features are labeled and notes attached. Most of these are nice additional labels, but are not relevant to the context in which the figure is used in this part of this chapter.

Figure 15.2.5

This is a series of three block diagrams.

The uppermost block diagram, labeled A, is of the non-extended crust with dashed lines on the top of the block indicating where faulting will occur.

The middle block diagram, labeled B and titled “Developing normal faults with extensional basins”, shows the area under extension as indicated by the arrows pulling the block in opposite directions. The block has also become thinner and longer if you compare its current outline to its older outline as indicated by the dashed former block boundary. The top of the block is cut by normal faults that dip to the right (east) and also form tilted east-dipping fault blocks, like leaning dominos. The upper right or eastern side of each fault block is elevated to form a ridge, while the lower, left or western side is now at the bottom of a valley. Arrows within the block show ductile, lower crust is rising under the tilted fault blocks helping them uplift.

The lower block diagram, labeled C, is the same physical situation as in the B or middle block diagram, except that the extension and thinning of the crust has become more extreme and the tilt of the faults has increased while the dip of the faults has lessened. This block diagram is titled “Upper crust fault block rotation”, which can be seen because the dip of the faults is now less than it was in block diagram B.  Or, if you consider the fault blocks as dominos, the dominos are now more tilted in block diagram C than they were in block diagram B.  

Figure 15.4.2

An aerial photo of the mouth of the Santa Ana River at the Pacific Ocean with Santa Catalina Island on the horizon. The main river channel is indicated on the photo with multiple levee breaks and flood waters rushing out. Also labeled are US Hwy 101 and major streets, all flooded.

Video 15.1.1

This video is a cartoon with no narrative. It’s a cross-section of a slope facing the ocean. Sea level falls and eventually stabilizes and becomes constant. The image pans in and sea level is at the bottom corner of the image. The wave action then cuts into and erodes the slope forming a wave-cut platform. Sea level rises again, and the wave-cut platform is submerged. Sea level stabilizes and the waves erode a new wave-cut platform on the slope above the submerged one.

The image pans in again and the first or lower, submerged wave-cut platform is no longer in the image. The second wave-cut platform is now at the top of the image, not submerged and has become a marine terrace. The land now starts to rise, and sea level now appears to fall until it is no longer visible. The land continues to uplift.

Sea level now rises again, but the land continues to rise also, so sea level does not submerge the marine terrace; instead, the waves start to erode another wave-cut platform below the marine terrace. The land continues to rise, and sea level appears to fall. The second wave-cut platform becomes a second marine terrace, below the upper one. The land continues to rise and eventually sea level also rises to a point below the lower marine terrace and the waves start to erode yet another wave-cut platform. The land continues to rise, and sea level falls again. There are now three marine terraces on the slope in the image, looking like a series of stair steps on the slope.

The land stops rising, and development occurs on the three marine terraces. They are covered with buildings and trees. Sea level now rises again to a level below the bottom of the third or lowest marine terrace. The waves begin to erode a new wave-cut platform, but they also undercut the slope of the lowest marine terrace, and a landslide occurs. The buildings at the edge of the slope are destroyed as they fall onto the wave-cut platform below.

Video 15.1.2

This video is of a drone flight at Corona Del Mar State Beach. There is no narration, but music plays throughout the flight.

The drone approaches the coast from the sea and heads toward sea stacks supporting an arch. It dives into and through the arch and over a wave-cut platform towards the cliff face of a marine terrace heading straight for the drone operator. The cliff face is approximately four to five times the height of the drone operator.

It banks to the right and another arch along the cliff face comes into view and the drone dives and heads through it, coming out the other side to fly parallel to the coast over more wave-cut platforms towards a large sea stack.

As the sea stack approaches, the drone rises and flies over it and turns right towards the coast and makes a U-turn and flies back parallel to the coast over the wave-cut platforms again then banks left towards the original sea stack and arch and flies back through it in the opposite direction, heading out to sea.

It then banks again as it rises up and the immediate coastline is revealed to be a series of small pocket beaches with wave-cut platforms and tidepools off each headland separating the small beaches. The drone then dives and for the third time travels through the sea arch, but this time, it banks to the left rather than the right.

It heads across the wave-cut platform and continues to bank left out to sea making another U-turn. As if flies past the sea stack, a flock of sea birds are visible perched on the seaward side of the sea stack.

It circles around and once again flies through the arch. It then banks left as it approaches the cliff face of the marine terrace and again flies past the sea stack with the perching sea birds and then flies around and through the arch a fifth and last time.

Video 15.3.2

During the Jurassic, subduction of the Farallon plate was occurring off the coast of the North American plate and volcanoes formed in what is now Sonora, Mexico.

By the Eocene, the volcanoes had eroded, and their sediment was being transported by rivers and streams to the Pacific Ocean and was washed out to sea and deposited in a submarine fan.

In the late Cenozoic, the plate boundary in southern California transitions from a subduction zone to a transform fault boundary and northward movement on strike-slip faulting begins. An area being moved by the fault northwards starts to slowly rotate clockwise and it includes the lower part of the submarine fan deposits of the Poway Group Cobbles. Movement on the strike-slip faults also displaces the upper part of the submarine fan deposits and the river and stream channels to the northwest.

The upper part of the submarine fan and river and stream channels will end up in today’s San Diego county as part of the Poway Group. The lower part of the submarine fan becomes part of the Transverse Ranges province as it is moved northwest and rotated into its current position.

The submarine fan deposits are found today as outcrops in the northern Channel Islands.

Video 15.4.1

The video begins with a fault map/fault model of the state of California. Faults are represented in three dimensions as planes dangling down into the Earth. Suddenly, the locations of scattered cities also appear on the map and the video zooms in to display the local area of the Newport-Inglewood fault. The fault segment that is going to break is highlighted in yellow on Earth’s surface and the other faults in the area are represented by white mesh planes. The surrounding local faults then disappear from the map while the Newport-Inglewood fault remains. The major freeways are now added to the map.

Suddenly the world changes perspective and tips up on end so that the view is a cross-section into the Earth with the Newport-Inglewood fault highlighted as a yellow mesh plane extending down. The picture then rotates 180° displaying the fault plane in three-dimensions. The model then dips and swings back to map-view. As it swings to map view, color starts to appear on the surface representing the damage done by the imaginary earthquake. The map comes to a stop, and a colored legend for damage according to the Mercalli Intensity scale is displayed. The scale ranges through, weak, light, moderate, strong, very strong, and finally severe. The terms weak, strong and severe are shown on the scale, others are implied by the color transitions.

Damage is as follows: An oval shaped ‘bull’s eye” has appeared with severe shaking at the center, gradationally changing to weak shaking with distance from the fault. Damage is only indicated on land, areas underwater are not color coded for damage.

Areas of severe shaking surround the fault and extend across greater metropolitan Los Angeles from the Santa Monica Mountains south to the Los Angeles-Orange county line and from the coast inland to I-5.

Very strong shaking surrounds the severe shaking, starting at the coast near Malibu, up and across the Santa Monica Mountains, to the Santa Susanna Mountains, the San Fernando Valley, over the Verdugo Hills, around through Pasadena, the western Chino hills and northern Santa Ana Mountains, down and across the Santa Ana River plain including the cities of Santa Ana and Anaheim, to the north of the San Joaquin Hills on the coast near Newport Beach.

Strong shaking extends from Malibu to Point Dume and swings up through the Santa Monica Mountains and the Westlake Village area to the Susana Mountains, the Simi Valley and the Santa Clarita Valley. Then down the western San Gabriel Mountains over as far as Sierra Madre and down past the eastern Chino Hills near Prado Dam, into the northern Santa Ana Mountains again and down including Irvine and the San Joaquin Hills and offshore near Laguna Beach.

Light to moderate shaking extends over past Oxnard to near Ventura, up and around and through the Santa Susana Mountains, over the northwestern San Gabriel Mountains towards Lancaster in the High Desert and down through the San Gabriel Mountains to Rancho Cucamonga and south along the I-15 and into the Santa Ana Mountains just west of Corona-east of Riverside, south through the mountains to come out near the coast south of San Clemente near the San Diego county line. Santa Catalina island is also colored for light to moderate shaking.

Weak shaking covers the rest of the image, west towards Santa Barbara, north into the High Desert, east toward San Bernardino, and South towards San Diego. All of these cities are just off the image.

Then the numbers appear for total fatalities, injuries, and damage.

If the earthquake occurred at 2 am local time, fatalities and injuries estimated at 9,589, concentrated in the area of severe shaking.

If the earthquake occurred at 2 pm local time, fatalities and injuries estimated at 15,430, concentrated in the areas of severe to very strong shaking.

If the earthquake occurred at 5 pm local time, fatalities and injuries estimated at 12,158, concentrated in the areas of severe, very strong, or strong shaking to the south.

Damage is estimated at $44.2 billion and includes the entire greater Los Angeles-Orange county metropolitan area as far west as Ventura, north to the Santa Clarita Valley, east to Corona, and south to Laguna Beach.

Video 15.4.2

The video begins with a fault map/fault model of the state of California. Faults are represented in three dimensions as planes dangling down into the Earth. Suddenly, the locations of scattered cities also appear on the map and the video zooms in to display the local area of the San Joaquin fault. The fault segment that is going to break is highlighted in yellow on Earth’s surface and the other faults in the area are represented by white mesh planes. The surrounding local faults then disappear from the map while the San Joaquin fault remains. The major freeways are now added to the map.

Suddenly the world changes perspective and tips up on end so that the view is a cross-section into the Earth with the San Joaquin fault highlighted as a yellow mesh plane extending down. The picture then rotates 180° displaying the fault plane in three-dimensions. The model then dips and swings back to map-view. As it swings to map view, color starts to appear on the surface representing the damage done by the imaginary earthquake. The map comes to a stop, and a colored legend for damage according to the Mercalli Intensity scale is displayed. The scale ranges through, weak, light, moderate, strong, very strong, and finally severe. The terms weak, strong and severe are shown on the scale, others are implied by the color transitions.

Damage is as follows: An oval shaped ‘bull’s eye” has appeared with severe shaking at the center, gradationally changing to weak shaking with distance from the fault. Damage is only indicated on land, areas underwater are not color coded for damage.

Areas of severe shaking surround the fault and extend up the coast to approximately the Bolsa Chica State Beach, inland to Santa Ana and extend to the foothills of the Santa Ana Mountains. Then continue south along the mountain front to Rancho Santa Margarita, and around and to the coast at San Clemente.

Very strong shaking surrounds the severe shaking, starting at the coast near Seal Beach, inland to Norwalk, then Brea, curves through Chino Hills State Park, south along the spine of the Santa Ana Mountains, and to the coast near Camp Pendleton.

Strong shaking extends from the coast near the Ocean Trails Reserve on the Palos Verde Peninsula, to downtown Los Angeles, along the I-10 eastward to the I-15 in Rancho Cucamonga, curves south, east of Norco, and down through Lake Elsinore. It continues south along the I-15 corridor to Murrieta, and then south to Oceanside. The eastern half of Santa Catalina Island also experiences strong shaking.

Light to moderate shaking extends inland from the coast at Santa Monica and north across the Santa Monica Mountains into the San Fernando Valley, curves over the Verdugo Hills and along the mountain front of the San Gabriel Mountains past Cajon Pass and the City of San Bernardino to Beaumont. From there light to moderate shaking continues south along the San Jacinto Mountain foothills to Warner Springs, and then down to just north of San Diego.

Weak shaking covers the rest of the image; therefore it extends beyond Thousand Oaks, north into the High Desert Region, beyond Palm Springs, and south of the US-Mexican border, and all of these areas are just off the image.

Then the numbers appear for total fatalities, injuries, and damage.

If the earthquake occurred at 2 am local time, fatalities and injuries estimated at 4,104 concentrated in the innermost area of severe shaking.

If the earthquake occurred at 2 pm local time, fatalities and injuries estimated at 8,008, concentrated in the area of severe shaking.

If the earthquake occurred at 5 pm local time, fatalities and injuries estimated at 6,057, concentrated in the areas of severe, very strong, to strong shaking.

Damage is estimated at $24.1 billion and includes all of Orange county and north and east into Los Angeles and Riverside counties.

Video 15.4.3

The video begins with a fault map/fault model of the state of California. Faults are represented in three dimensions as planes dangling down into the Earth. Suddenly, the locations of scattered cities also appear on the map and the video zooms in to display the local area of the Palos Verde fault offshore between Santa Catalina Island and Orange county, paralleling the Newport-Inglewood fault. The fault segment that is going to break is highlighted in yellow on Earth’s surface and the other faults in the area are represented by white mesh planes. The surrounding local faults then disappear from the map while the Palo Verde fault remains. The major freeways are now added to the map.

Suddenly the world changes perspective and tips up on end so that the view is a cross-section into the Earth with the Palos Verde fault highlighted as a yellow mesh plane extending down. The picture then rotates 180° displaying the fault plane in three-dimensions. The model then dips and swings back to map-view. As it swings to map view, color starts to appear on the surface representing the damage done by the imaginary earthquake. The map comes to a stop, and a colored legend for damage according to the Mercalli Intensity scale is displayed. The scale ranges through, weak, light, moderate, strong, very strong, and finally severe. The terms weak, strong and severe are shown on the scale, others are implied by the color transitions.

Damage is as follows: The Palos Verdes fault is offshore and a line of severe shaking has appeared along the coast, gradationally changing to weak shaking with distance from the coast. Damage is only indicated on land, areas underwater are not color coded for damage.

A line of severe shaking appears along the coast from Seal Beach to Newport Beach.

Very strong shaking surrounds the severe shaking, starting at the coast near Long Beach, extending up and over towards Compton, curving eastwards across I-5 to Brea, down to Anaheim and over to the mountain front of the Santa Ana Mountains. It extends past Irvine and then down to Laguna Beach. Very strong shaking is also experienced in the area around Avalon on Santa Catalina Island.

Strong shaking extends inward from the coast near LAX, curving around and up the image to downtown Los Angeles, across and around to Whittier, down to Brea and into Anaheim Hills. Then south along the mount front of the Santa Ana Mountains to Trabuco Canyon, along the spine of the Santa Ana Mountains, curving south and offshore south of Oceanside. Most of the rest of San Catalina Island also experiences strong shaking.

Light to moderate shaking extends inland north of Santa Monica and over the Santa Monica Mountains into the San Fernando Valley and north off the image. It reappears on the image in the San Gabriel Mountains past the Verdugo Hills and then along the San Gabriel Mountain from almost to Rancho Cucamonga. It then follows the I-15 corridor south and off the image.

Weak shaking covers the rest of the image, west and north from Malibu, and east of the I-15 corridor.

Then the numbers appear for total fatalities, injuries, and damage.

If the earthquake occurred at 2 am local time, fatalities and injuries estimated at 367, concentrated in the severe shaking area, right on the coast.

If the earthquake occurred at 2 pm local time, fatalities and injuries estimated at 397, concentrated in the areas of severe to strong shaking closer to the coast.

If the earthquake occurred at 5 pm local time, fatalities and injuries estimated at 338, concentrated in the areas of severe to strong shaking closer to the coast.

Damage is estimated at $3.14 billion and includes the entire greater Los Angeles-Orange-San Diego county metropolitan area from Torrance and Compton in Los Angeles county south to Oceanside in San Diego county. Maximum damage is in Orange county from Seal Beach to Newport Beach.

Video 15.4.4

The video begins with a fault map/fault model of the state of California. Faults are represented in three dimensions as planes dangling down into the Earth. Suddenly, the locations of scattered cities also appear on the map and the video zooms in to display the local area of the Rose Canyon fault. The fault segment that is going to break is highlighted in yellow on Earth’s surface and the other faults in the area are represented by white mesh planes. The surrounding local faults then disappear from the map while the Rose Canyon fault remains. The major freeways are now added to the map.

Suddenly the world changes perspective and tips up on end so that the view is a cross-section into the Earth with the Newport-Inglewood fault highlighted as a yellow mesh plane extending down. The picture then rotates 180° displaying the fault plane in three-dimensions. The model then dips and swings back to map-view. As it swings to map view, color starts to appear on the surface representing the damage done by the imaginary earthquake. The map comes to a stop, and a colored legend for damage according to the Mercalli Intensity scale is displayed. The scale ranges through, weak, light, moderate, strong, very strong, and finally severe. The terms weak, strong and severe are shown on the scale, others are implied by the color transitions.

Damage is as follows: An oval shaped ‘bull’s eye” has appeared with severe shaking at the center, gradationally changing to weak shaking with distance from the fault. Damage is only indicated on land, areas underwater are not color coded for damage.

Areas of severe shaking surround the fault and extend north to Encinitas and across to the I-15 corridor, then south just past the I-15 and I-8 corridor into Mexico.

Very strong shaking surrounds the severe shaking, starting at the coast near Oceanside, curving north and inland to Fallbrook, over towards Pala and then south into Mexico.

Strong shaking extends from north of Camp Pendleton, over to the spine of the mountains, south through Otay lake into Mexico.

Light to moderate shaking extends north and off the image and south on a line through Mt. Palomar and Alpine into Mexico.

Weak shaking covers the rest of the image east of a line through Borrego Springs and Campo.

Then the numbers appear for total fatalities, injuries, and damage.

If the earthquake occurred at 2 am local time, fatalities and injuries estimated at 366, concentrated in the area of severe shaking around Mission Bay and Imperial Beach.

If the earthquake occurred at 2 pm local time, fatalities and injuries estimated at 345, concentrated in the areas of severe shaking around Mission Bay, Old Town, and Kearny Mesa.

If the earthquake occurred at 5 pm local time, fatalities and injuries estimated at 308, concentrated in the areas of severe shaking around Mission Bay, Old Town, and Kearny Mesa.

Damage is estimated at $4.22 billion and includes the entire greater San Diego area south from Torrey Pines to the US-Mexican border and inland to eastern extent of the I-15 / I-805 corridor.

Video 15.4.5

The video begins with a fault map/fault model of the state of California. Faults are represented in three dimensions as planes dangling down into the Earth. Suddenly, the locations of scattered cities also appear on the map and the video zooms in to display the local area of the Elsinore fault. The fault segment that is going to break is highlighted in yellow on Earth’s surface and the other faults in the area are represented by white mesh planes. The surrounding local faults then disappear from the map while the Elsinore fault remains. The major freeways are now added to the map.

Suddenly the world changes perspective and tips up on end so that the view is a cross-section into the Earth with the Elsinore fault highlighted as a yellow mesh plane extending down. The picture then rotates 180° displaying the fault plane in three-dimensions. The model then dips and swings back to map-view. As it swings to map view, color starts to appear on the surface representing the damage done by the imaginary earthquake. The map comes to a stop, and a colored legend for damage according to the Mercalli Intensity scale is displayed. The scale ranges through, weak, light, moderate, strong, very strong, and finally severe. The terms weak, strong and severe are shown on the scale, others are implied by the color transitions.

Damage is as follows: An oval shaped ‘bull’s eye” has appeared with severe shaking at the center, gradationally changing to weak shaking with distance from the fault. Damage is only indicated on land, areas underwater are not color coded for damage.

Areas of severe shaking surround the fault and extend from Corona towards Riverside curving down to Perris and over to Wildomar. Then across the Santa Ana Mountains to Mission Viejo, up the Santa Ana Mountain front through villa Park and Anaheim Hills over to Corona.

Very strong shaking surrounds the severe shaking, coming onshore near Huntington Beach, curving up to Montebello and over to near the I-10 and I-15 interchange, along the I-10 to Loma Linda, and then through the San Timoteo Badlands swings down and around to Murrieta, across the San Ana Mountains, and offshore near Dana Point.

Strong shaking comes onshore near Long Beach, then up to the downtown Los Angeles area, swings east along the San Gabriel Mountain front and into the mountains near Claremont. Over the mountains towards Wrightwood and then curves east toward Cajon Pass and along the San Bernardino Mountain front to Mentone. From there it is south to Anza and around to Palomar Mountain, and offshore near Oceanside.

Light to moderate shaking comes onshore near Santa Monica and north across the Santa Monica Mountains into the San Fernando Valley, across the San Gabriel Mountains to near Pear Blossom and the off the image. Light to moderate shaking then reappears on a line down through Lucerne, around to the San Jacinto Pass, and down the eastern mountain front of the San Jacinto Mountains into Mexico.

Weak shaking covers the rest of the image, west of Malibu and east of Palm Springs to Borrego Springs down into Mexico.

Then the numbers appear for total fatalities, injuries, and damage.

If the earthquake occurred at 2 am local time, fatalities and injuries estimated at 236, concentrated in the area of severe shaking.

If the earthquake occurred at 2 pm local time, fatalities and injuries estimated at 220, concentrated in the area of severe damage in the Santa Ana River Canyon or in the area of very strong shaking along the Santa Ana River southwest of Santa Ana.

If the earthquake occurred at 5 pm local time, fatalities and injuries estimated at 1,207, concentrated in the area of severe shaking in the Santa Ana River Canyon or in the area of very strong shaking along the Santa Ana River southwest of Santa Ana.

Damage is estimated at $2.21 billion and includes the Corona-Norco-Riverside corridor along the I-15, the Santa Ana River Canyon, greater Santa Ana area and the Dana Point-San Clemente area.