Ground Crack Earthquake

[Albertina Drybread]

Earthquakesare recorded by instruments called seismographs. The recording they make is called a seismogram. The seismograph has a base that sets firmly in the ground, and a heavy weight that hangs free. When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not. Instead the spring or string that it is hanging from absorbs all the movement. The difference in position between the shaking part of the seismograph and the motionless part is what is recorded.

The size of the earthquake is called its magnitude. There is one magnitude for each earthquake. Scientists also talk about theintensity of shaking from an earthquake, and this varies depending on where you are during the earthquake.

P waves are like the lightning, and S waves are like the thunder. The P waves travel faster and shake the ground where you are first. Then the S waves follow and shake the ground also. If you are close to the earthquake, the P and S wave will come one right after the other, but if you are far away, there will be more time between the two.

Scientists then use a method called triangulation to determine exactly where the earthquake was (see image below). It is called triangulation because a triangle has three sides, and it takes three seismographs to locate an earthquake. If you draw a circle on a map around three different seismographs where the radius of each is the distance from that station to the earthquake, the intersection of those three circles is the epicenter!

No, and it is unlikely they will ever be able to predict them. Scientists have tried many different ways of predicting earthquakes, but none have been successful. On any particular fault, scientists know there will be another earthquake sometime in the future, but they have no way of telling when it will happen.

These are two questions that do not yet have definite answers. If weather does affect earthquake occurrence, or if some animals or people can tell when an earthquake is coming, we do not yet understand how it works.

ALL downloaded records are UNSCALED and as-recorded (UNROTATED). The scaling tool available on this site is to be used to determine the scale factors to be used in the simulation platform. These scale factors can be found with the record metadata in the download (Scaling the traces within this tool would only cause confusion with file versioning).

Please note that, due to copyright issues, a strict limit has been imposed on the number of records that can be downloaded within a unique time window. The current limit is set at approximately 200 records every two weeks, 400 every month. Abusive downloads will result in further restrictions.

The NGA-West2 ground motion database includes a very large set of ground motions recorded in worldwide shallow crustal earthquakes in active tectonic regimes. The database has one of the most comprehensive sets of meta-data, including different distance measure, various site characterizations, earthquake source data, etc. The current version of the database is similar to the NGA-West2 database, which was used to develop the 2014 NGA-West2 ground motion models (GMMs). peer.berkeley.edu/ngawest2

The objective of NGA-East is to develop a new ground motion characterization (GMC) model for the Central and Eastern North-American (CENA) region. The GMC model consists in a set of new ground motion models (GMMs) for median and standard deviation of ground motions (GMs) and their associated weights in the logic-trees for use in probabilistic seismic hazard analyses (PSHA). peer.berkeley.edu/ngaeast

The PEER NGA strong-motion databases, the associated flatfiles, reports, and products are subject to future revisions as a result of the review process, as new information is obtained, or as new interpretations are made.

The USGS collaborates with organizations that develop building codes (for buildings, bridges, and other structures) to make seismic design parameter values available to engineers. The design code developers first decide how USGS earthquake hazard information should be applied in design practice. Then, the USGS calculates values of seismic design parameters based on USGS hazard values and in accordance with design code procedures.

Due to insufficient resources and the recent development of similar web tools by third parties, the USGS has replaced its former U.S. Seismic Design Maps web applications with web services that can be used through third-party tools. Your options for using the replacement USGS web services,which still provide seismic design paramter values from numerous design code editions, are:

Earthquake-triggered ground failure, such as landsliding and liquefaction, can contribute significantly to losses, but our current ability to accurately include them in earthquake-hazard analyses is limited. The development of robust and widely applicable models requires access to numerous inventories of ground failures triggered by earthquakes that span a broad range of terrains, shaking characteristics, and climates. We present an openly accessible, centralized earthquake-triggered groundfailure inventory repository in the form of a ScienceBase Community to provide open access to these data with the goal of accelerating research progress. The ScienceBase Community hosts digital inventories created by both U.S. Geological Survey (USGS) and non-USGS authors. We present the original digital inventory files (when available) as well as an integrated database with uniform attributes. We also summarize the mapping methodology and level of completeness as reported by the original author(s) for each inventory. This document describes the steps taken to collect, process, and compile the inventories and the process for adding additional ground-failure inventories to the ScienceBase Community in the future.

Earthquake-triggered landslides and liquefaction, collectively referred to as ground failure, can be a significant contributor to earthquake losses. The USGS Ground Failure (GF) earthquake product provides near-real-time spatial estimates of earthquake-triggered landslide and liquefaction hazard following significant earthquakes worldwide.

We developed this product to provide initial awareness of the overall extent and importance of potential landslides and liquefaction, and to indicate areas in which they are most likely to have occurred. It takes time for first responders and experts to survey the actual damage in the area, so our product provides early estimates of where to focus attention and response planning. Though our models provide regional estimates of landslide and liquefaction hazard triggered by this earthquake, they do not predict specific occurrences.

The GF product is based on a suite of geospatial models that relate ground motion estimates provided by the USGS ShakeMap and proxies for ground failure susceptibility to rapidly provide regional estimates of earthquake-triggered ground failure hazard over a grid of evenly-spaced points. See Models section for details.

The GF product is generally triggered when a USGS ShakeMap is created for earthquakes greater than M5 within the United States and greater than M6 worldwide. It can also be triggered manually. Results are always shown if it is run, even for events for which little to no ground failure is estimated. However, a pending status may sometimes be reported for significant events undergoing manual ShakeMap review. This means no GF alert levels will be reported until that review is done. Although the maps will still be available, the preliminary nature of the shaking inputs should be considered when interpreting the ground failure results.

Selecting the Ground Failure card takes the user to the Summary page for Ground Failure. This page gives the user an overview of the hazard and population exposure for the two different types of ground failure and allows the user to navigate to interactive maps and other features, as described in the following sections and labeled in Figure 2.

The top of all earthquake event webpages consists of a summary of the most up-to-date earthquake information (magnitude, geographic location, event time, and epicentral location). Below this is the title of the product and time of last update.

This tab provides basic information for the general public that describes why we developed this product, how to use it, what earthquake-triggered landslides and liquefaction are, and what hazards they pose to human populations. The simplified information provided in this tab is intended for non-expert users who may not be interested in the level of detail provided on this detailed webpage.

The left column of the summary webpage summarizes the landslide hazard and exposure alert levels for this earthquake based on our preferred landslide model, and the right column corresponds to the same for liquefaction. On mobile devices, these columns will be stacked on top of each other.

The alert level bins are each defined by a qualitative order-of-magnitude range for each statistic, which were chosen based on historic earthquakes with known consequences. See the Alert Level Definitions section for details.

A footer appears at the bottom of all Ground Failure product pages with basic disclaimers about the product and a link to a static webpage that provides detailed technical information for advanced users (this webpage).

The Downloads expansion panel allows advanced users to download GIS files of all ground failure model results, including the alternative model results, which are not currently shown on the interactive map.

The GF models are designed to be rapidly and consistently applicable in any region of the world, requiring that they be relatively simple and depend on globally-available input datasets. There are many factors that contribute to a given occurrence of ground failure that are unknowable at the global scale; thus the models are not able to account for local characteristics of topography or geology nor to predict specific occurrences.

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