This mapping application illustrates earthquake epicenters within the state of Ohio and numerous border-region earthquakes. The map is searchable using several parameters, including magnitude and year.
Reading the Map
Earthquake epicenters are represented by blue and red dots. Clicking a dot will open a window that provides detailed information about that earthquake, including magnitude, depth, and date and time.
- Blue dots depict epicenters for historically located earthquakes, before the advent of seismic instrument recording, and may not reflect actual epicenter locations. For more information, see Open-File Report 2017-01.
- Red dots denote instrumentally located earthquakes from differing networks through time, such as the U.S. Geological Survey and the Ohio Seismic Network, beginning in 1999.
Earthquake magnitudes are denoted by several seismic scales, such as Ml (Richter, adjusted for locality), Md (Duration magnitude), and Mw (Moment magnitude). Modified Mercalli Intensities are also provided. For more information on earthquake magnitude types calculated for seismic events in Ohio, see below.
Earthquake depths are approximate and given in kilometers (km) below the land surface.
Seismometer station locations for the current Ohio Seismic Network (2016–present day) are denoted by yellow stars; locations are approximate. Station elevations are provided in meters (m) relative to sea level.
Magnitude Type: Mwr (regional)
Magnitude Range: ~4.0 to ~6.5
Distance Range: 0–10 degrees
Equation: Mw = 2/3 ✕ (log10(Mo) − 16.1), where Mo is the seismic moment.
Based on the scalar seismic moment of the earthquake, derived from moment tensor inversion of the whole seismogram at regional distances (~10–100 s; pass band based on size of EQ). Source complexity and dimensions at larger magnitudes (~M7.0 or greater) generally limits applicability. Authoritative for <M5.0. Within the continental U.S. and south-central Alaska, where the U.S. Geological Survey (USGS) has a large number of high-quality broadband stations, expect computations of an Mwr consistently for events as small as M4.0. In some areas of the country, with relatively dense broadband coverage, USGS can compute Mwr consistently to as small as M3.5.
ML / Ml / ml
Magnitude Type: ML Ml, or ml (local)
Magnitude Range: ~2.0 to ~6.5
Distance Range: 0–600 km
The original magnitude relationship defined by Richter and Gutenberg in 1935 for local earthquakes. It is based on the maximum amplitude of a seismogram recorded on a Wood-Anderson torsion seismograph. Although these instruments are no longer widely in use, ML values are calculated using modern instrumentation with appropriate adjustments. Reported by the National Earthquake Information Center (NEIC) for all earthquakes in the U.S. and Canada. Only authoritative for smaller events, typically M<4.0, for which there is no mb or moment magnitude. In the central and eastern U.S., NEIC also computes ML but restricts the distance range to 0–150 km. In that area, it is only authoritative if there is no mb_Lg as well as no mb or moment magnitude.
mb_Lg / mb_lg / MLg
Magnitude Type: mb_Lg, mb_lg, or MLg (short-period surface wave)
Magnitude Range: ~3.5 to ~7.0
Distance Range: 150–1,110 km (10 degrees)
A magnitude for regional earthquakes based on the amplitude of the Lg surface waves as recorded on short-period instruments. Only authoritative for smaller events in the central and eastern U.S., typically <4.0, for which there is no mb or moment magnitude.
Md / md
Magnitude Type: Md or md (duration)
Magnitude Range: ~4 or smaller
Distance Range: 0–400 km
Based on the duration of shaking as measured by the time decay of the amplitude of the seismogram. Sometimes the only magnitude available for very small events. Often used (especially in the past) to compute magnitude from seismograms with "clipped" waveforms due to limited dynamic recording range of analog instrumentation, which makes it impossible to measure peak amplitudes. Computed by NEIC but only published when there is no other magnitude available.